Working Through the Data Conundrum: 

Identifying People with Intellectual and 

Developmental Disabilities in National 

Population Surveys 

 

 

Administration on Intellectual and Developmental Disabilities 

Administration for Community Living 

September, 2019 

Citation: Havercamp, S.M., Krahn, G., Larson, S., Weeks, J.D. and the National Health 

Surveillance for IDD Workgroup (2019). Working Through the IDD Data Conundrum: Identifying 

People with Intellectual Disability and Developmental Disabilities in National Population Surveys. 

Washington, DC: Administration on Intellectual and Developmental Disabilities.
Identifying People with IDD in National Surveys

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Collaborating Partners within the United States Department of Health & 

Human Services

Administration on Intellectual and Developmental Disabilities, Administration for Community 

Living (AIDD/ACL)

Center for Medicaid and Children’s Health Insurance Program Services, Centers for Medicare & 

Medicaid Services (CMCS/CMS)

Center for Clinical Standards and Quality, Centers for Medicare & Medicaid Services (CCSQ/CMS)

National Center for Health Statistics, Centers for Disease Control & Prevention (NCHS/CDC)

Assistant Secretary for Planning and Evaluation, United States Department of Health & Human 

Services (ASPE/HHS)

National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control & 

Prevention (NCBDDD/CDC)

National Institute for Disability, Independent Living and Rehabilitation Research, Administration 

for Community Living (NIDILRR/ACL)

Office of Minority Health, Centers for Medicare & Medicaid Services (OMH/CMS)

Office of Minority Health, United States Department of Health & Human Services (OMH/HHS)
Identifying People with IDD in National Surveys

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Members of the National Health Surveillance for Intellectual and 

Developmental Disabilities Workgroup

Susan M. Havercamp (Chair), Ohio State University

Gloria Krahn (Co-Chair), Oregon State University

Julie D. Weeks, National Center for Health Statistics, CDC, HHS

Alissa Cyrus, National Center on Birth Defects and Developmental Disabilities, CDC, HHS

Ellen Blackwell, Centers for Medicare & Medicaid Services, HHS

John Drabeck, Assistant Secretary for Planning and Evaluation, HHS

Glenn Fujiura, University of Illinois at Chicago

Melissa Harris, Centers for Medicare & Medicaid Services, HHS

Natasha Hollis, National Center on Birth Defects and Developmental Disabilities, CDC, HHS

Barbara Kornblau, Coalition for Disability Health Equity

Helen Lamont, Assistant Secretary for Planning and Evaluation, HHS

Sheryl Larson, University of Minnesota 

Bill Martin, Assistant Secretary for Planning and Evaluation, HHS

With contributions from:

Jennifer Madans, National Center for Health Statistics, CDC, HHS

Tawara Goode, Georgetown University

Dianne Rucinski, Office on Minority Health, HHS

Hassan Ragy, Human Services Research Institute

Administration for Community Living staff:

Jennifer Johnson, Administration on Intellectual and Developmental Disabilities, ACL, HHS

Andrew Morris, Center for Policy and Evaluation, ACL, HHS

Amanda Reichard, National Institute on Disability, Independent Living, and Rehabilitation 

Research, ACL, HHS

Kristen Robinson, Center for Policy and Evaluation, ACL, HH
Identifying People with IDD in National Surveys

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Acknowledgements

I am pleased to present this report “Working through the Data Conundrum: Identifying People

with Intellectual and Developmental Disabilities in National Population Surveys.” This report 

results from a highly productive partnership of public agencies and private individuals to address 

the need for better health surveillance data on people with intellectual and developmental 

disabilities, a problem that has been recognized since the Surgeon General‘s 2001 report. 

This report builds on previous work of HHS. Most notable is the work of the National Center on

Birth Defects and Developmental Disabilities of the Centers for Disease Control and Prevention

(CDC) with their early and ongoing focus to identify the health promotion needs of this 

population and that of the National Center for Health Statistics, CDC, which provides

international leadership on improving health surveillance of all populations. 

To ensure quality of life for individuals with intellectual and developmental disabilities, it is 

critical that we continue to advance discussions and efforts around health surveillance for this 

highly diverse population. We hope that this report and the work behind it will lead the nation 

forward in ensuring policies and programs are in place that support people with intellectual and 

developmental disabilities to live with respect and dignity as fully participating members of their 

communities.

I’m deeply thankful for the collaborations with the other HHS agencies who committed their 

effort and attention to this initiative. These include the CDC’s NCHS and NCBDDD; ACL’s NIDILRR

and AIDD staff; HHS’s ASPE; and CMS’s CMCS, CCSQ and OMH. The work was facilitated and 

enriched by the contributions of researchers and disability organizations that contributed 

generously with their time under the leadership of Susan Havercamp and Gloria Krahn. Finally, 

I’d like to acknowledge the contributions of Andrew Morris of CPE, ACL, who provided the 

internal management and coordination that brought this report to completion. 

Jennifer Johnson, EdD

Deputy Commissioner, Administration on Disabilities and 

Director, Office of Disability Service Innovations
Identifying People with IDD in National Surveys

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Contents

Collaborating Partners within Health & Human Services.............................................................2

Members of the National Health Surveillance Workgroup..........................................................3

Acknowledgements............................................................................................................................4

Contents..............................................................................................................................................5

Acronyms.............................................................................................................................................7

Executive summary............................................................................................................................8

I. Introduction

 A. Estimating prevalence of ID.......................................................................................13

 B. Impetus for this report ..............................................................................................15

II. Background

A. Historical and legislative context.............................................................................17

B. Conceptualizations of disability...............................................................................19

C. Defining intellectual and developmental disabilities..............................................20

i. Developmental Disabilities..................................................................21

ii. Intellectual Disability ...........................................................................22

iii. Comparing ID and DD..........................................................................23

D. Past approaches to measuring IDD.........................................................................24

i. Function vs Diagnosis..........................................................................24

ii. Single Questions or Multiple Question-Sets.......................................25

iii. Self and Proxy Reporting .....................................................................25

III. Surveillance Gaps and Strategies for Identifying IDD Respondents in Population-Based Surveys

A. Limitations of current disability identification questions .....................................26

B. Available survey data for adults and children with IDD........................................27

i. Adults with IDD in the U. S. .................................................................27

ii. Children with IDD in the U. S...............................................................28

C. Domains required to identify ID and DD ...............................................................29

i. Domains Required by the Definitions of ID and DD...............................29

ii. Domains that Best Predict IDD status.................................................32

D. Questions from other surveys that address needed domains..............................33

i. Survey of Income and Program Participation (1984-2013)....................33

ii. National Health Interview Survey Disability (1994-1995)... ...................34

iii. Essential domains to identify IDD for health surveillance.......................35

a. Learning......................................................................................35

b. Independent Living Skills............................................................36

c. Age of onset................................................................................37

iv. Additional Domains Needed for IDD Prevalence Estimates.................37

a. Communication..........................................................................37

b. Self-Direction..............................................................................38
Identifying People with IDD in National Surveys

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c. Expected Duration......................................................................40

IV. Methodological Considerations

A. Small sample sizes...................................................................................................41

B. Benchmarking .........................................................................................................41

C. Item development and cognitive testing ...............................................................42

D. Including racial, ethnic, and linguistically diverse populations..............................42

E. Data Collection in Territories.................................................................................44

V. Summary and Conclusions...................................................................................................45

VI. References...........................................................................................................................47

Appendices

A. Differentiating ID (AAIDD) and DD (DD Act) .........................................................55

B. Items on population surveys used to identify ID or DD .......................................57

Table B1: 2016 National Health Interview Survey ................................................58

Table B2: 1994-1995 NHIS Disability Survey .........................................................60

Table B3: Survey of Income and Program Participation: Adult.............................63

Table B4: Survey of Income and Program Participation: Child .............................65

Table B5: WHO Disability Assessment Schedule 2.0.............................................66

 
Identifying People with IDD in National Surveys

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Acronyms 

AAIDD American Association on Intellectual and Developmental Disabilities 

ACL Administration for Community Living, HHS

ACS American Community Survey

ADA Americans with Disabilities Act

ADDM Autism and Developmental Disabilities Monitoring 

ADL Activities of Daily Living

AIDD Administration on Intellectual and Developmental Disabilities, ACL, HHS

AI/AN American Indian/Alaska Native

ASD Autism Spectrum Disorder

ASPE Assistant Secretary for Planning and Evaluation, HHS

AUCD Association of University Centers on Disabilities

CCQDER Collaborating Center for Questionnaire Design and Evaluation Research 

CDC Centers for Disease Control & Prevention

CMS Centers for Medicare & Medicaid Services

CERIIDD Center for Epidemiological Research for Individuals with Intellectual and 

Developmental Disabilities

CP Cerebral Palsy

CPS Current Population Survey

DD Developmental Disabilities

DD Act Developmental Disabilities Assistance and Bill of Rights Act of 2000

HCBS Home & Community Based Services

HHS Health & Human Services, U.S. Department of

HRSA Health Resources and Services Administration 

HSRI Human Services Research Institute

IADL Instrumental Activities of Daily Living

ICDR Interagency Committee on Disability Research

ID Intellectual Disability

IDD Intellectual and Developmental Disabilities

LTSS Long-term Supports and Services

MCHB Maternal and Child Health Bureau, HRSA, HHS

MR Mental Retardation [term has been replaced by Intellectual Disability]

NACDD National Association of Councils on Developmental Disabilities

NASDDDS National Association of State Directors of Developmental Disabilities Services

NCHS National Center for Health Statistics, CDC

NCI National Core Indicators

NHIS National Health Interview Survey

NHIS-D National Health Interview Survey - Disability Survey (1994-1995)

NSCH National Survey of Children’s Health

OMH Office of Minority Health, CMS

OMH Office of Minority Health, HHS

SB Spina Bifida

SIPP Survey of Income and Program Participation
Identifying People with IDD in National Surveys

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Executive Summary 

 

Surveillance data allow policy analysts and population health researchers to track the size and 

nature of target populations, to identify health disparities, and to determine characteristics that 

contribute to health. However, for the population of people with intellectual and developmental 

disabilities (IDD), there is no national effort to collect such surveillance information. 

In an effort to better understand the health status and prevalence of people with IDD in the U.S., 

a workgroup comprised of key agencies within the U.S. Department of Health and Human 

Services (HHS) and other experts in the field of IDD convened during the first half of 2018 to 

review the current landscape and future directions related to surveillance for people with IDD. 

This paper describes the need for, availability of, and recommendations for changes in 

surveillance data about people with IDD, particularly adults. Priority criteria for identifying 

people with IDD relate to measurements of learning, independent living, and age of onset. 

Additional identifying criteria relate to measurements of communication, self-direction, and 

expected duration. This is one of two companion workgroup reports; the other report is

Enriching our Knowledge: State and Local Data to Inform Health Surveillance of the Population 

with Intellectual and Developmental Disabilities (2019).

The Data Conundrum 

Currently, there is no systemic national research effort addressing the prevalence and health 

status of adults with IDD. People with disabilities broadly defined are identifiable in a number of 

national surveys that include the American Community Survey (ACS, the Current Population 

Survey (CPS), and the Survey of Income and Program Participation (SIPP) using six standard 

disability items. However, the identification questions are too broad to be useful in identifying

people with IDD as based on statutory definitions used in federal government.
Identifying People with IDD in National Surveys

9

Several ongoing health surveillance programs monitor the prevalence in children of 

developmental disabilities (DD) and conditions associated with it such as intellectual disability

(ID), autism spectrum disorder (ASD), cerebral palsy (CP), epilepsy, and spina bifida. As 

examples, the CDC’s Autism and Developmental Disabilities Monitoring (ADDM) network 

surveillance program generates regularly updated prevalence estimates for ASD, ID, and CP in 8-

year-old children and ASD and ID in 4-year-old children. The National Health Interview Survey 

(NHIS) and the 2016 National Survey of Children’s Health (NSCH) are nationally representative 

population-based surveys that include questions suitable for identifying children with IDD ages 3 

to 17 years. Administrative prevalence estimates for IDD in children can be obtained through the 

National Center for Education Statistics at the United States Department of Education (Fast 

Facts: Students with Disabilities).

Several administrative data sets and projects provide surveillance data for adults with IDD. For 

example, an AIDD funded Project of National Significance, the State of the States in 

Developmental Disabilities (Braddock, Hemp, Tanis, Wu, and Haffer, 2017), provides yearly 

updates on the determinants of public spending and programmatic trends for IDD services in the 

50 states, the District of Columbia, and the United States as a whole. Administrative data from 

the Centers for Medicare & Medicaid Services (CMS) (Centers for Medicaire and Medicaid 

Services), the Office of Special Education and Rehabilitative Services (OSERS) at the U.S. 

Department of Education (OSERS Office of Special Education and Rehabilitative Services), and the 

Social Security Administration also allow analysts to identify and study people with IDD. 

Unlike for children, there are no ongoing national health surveillance systems that monitor the 

prevalence, characteristics, health needs, and health outcomes of adults with IDD, nor are there 

data that compare ID with DD. Historically, the 1994-1995 National Health Interview Survey -

Disability Survey (National Health Interview Survey) included a comprehensive set of items used 

by researchers to better understand the child and adult ID and DD populations, including 

prevalence estimates, general characteristics, health status, and health outcomes. The SIPP 

Social Security Administration Supplement from 2008 to 2013 included items to identify adult 
Identifying People with IDD in National Surveys

10

sample members with ID and/or DD. From 2012 to 2017, the NHIS included an item to identify 

adult sample members with ID but not adults with DD. Neither the SIPP nor the NHIS surveys 

currently include data elements sufficient to allow identification of adults with ID and DD.

Addressing the Data Conundrum 

Recognizing the need for current surveillance data on children and adults with ID and DD and the 

challenges to collecting such information, AIDD, in 2015, initiated discussions with a number of 

federal partners in HHS to explore potential solutions, including the use of NHIS. With pending 

changes to the NHIS and recent changes to SIPP, there are no national surveys that provide 

prevalence and health data for people with IDD. These discussions led AIDD to convene a multiagency, multi-stakeholder meeting in November 2017 with representatives from the HHS

agencies: Administration for Community Living (ACL), Assistant Secretary for Planning and 

Evaluation (ASPE), National Center for Birth Defects and Developmental Disabilities (NCBDDD) at 

the Centers for Disease Control & Prevention (CDC), Centers for Medicare & Medicaid Services

(CMS), National Center for Health Statistics (NCHS) at the CDC, and the HHS Office on Minority 

Health (OMH); the following national disability organizations: Association of University Centers 

on Disabilities (AUCD), Center for Epidemiological Research for Individuals with Intellectual and 

Developmental Disabilities (CERIID), Human Services Research Institute (HSRI), National 

Association of Councils on Developmental Disabilities (NACDD), and National Association of State 

Directors of Developmental Disability Services (NASDDS); and a number of university-based

disability researchers. Following the November 2017 meeting, two workgroups were established, 

one of which was the AIDD National Health Surveillance Workgroup. The charge for this 

workgroup was to identify existing and suggest new survey questions to supplement the data 

currently being collected in national survey programs such as the NHIS so that the prevalence of 

children and adults with IDD could be better estimated. 

This technical report is the final product of the AIDD National Health Surveillance Workgroup. 

This document provides historical context and alternative conceptualizations that underlie 

approaches to measuring IDD, describes ID and DD using enabling legislation and professional 
Identifying People with IDD in National Surveys

11

practice guidelines, and discusses currently available prevalence estimates for IDD in children 

and adults. This report identifies gaps in current surveillance efforts for adults with IDD and 

proposes strategies for national survey programs to better identify community-dwelling adults 

with IDD so that researchers and policy makers have access to data that represent the 

noninstitutionalized U.S. population. The report is meant to extend beyond the IDD population

currently served by Medicaid DD services to include all people with IDD. 

The report identifies the key constructs that must be measured to identify sample members with 

IDD, estimate prevalence rates, and enable current data collection systems to study the health 

status, outcomes, and unmet needs of this population. These include the minimal questions to 

be included in population surveys to identify this population, suggests additional domains to fully 

capture people with IDD for incidence and prevalence estimates, and suggests directions for 

more comprehensive surveillance of people with IDD. The report closes with a brief review of 

methodological considerations regarding item development, cognitive testing, and the 

importance of cultural sensitivity in attending to cultural and linguistic differences within this 

population to ensure health equity. 

Directions for Future Activities: 

1. AIDD/ACL and its partners are working with the research staff at the National Center for 

Health Statistics Collaborating Center for Questionnaire Design and Evaluation Research

(CCQDER) to construct and cognitively test survey questions that are valid, reliable, and 

appropriate for people with IDD, including those from racially and ethnically diverse 

backgrounds. These questions are intended for future use in the NHIS and other surveys 

to identify respondents with IDD.

2. Once updated and benchmarked, prevalence estimates collected at regular survey 

iterations can guide future fiscal projections, policy development, and program planning. 

As statutes are changed, the domains to be measured may need to be updated.

3. Continued collaboration will be needed across federal agencies and stakeholder groups if

health surveillance practices are to be broadly implemented across national data 
Identifying People with IDD in National Surveys

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collection systems to enable better identification and prevalence estimates of children 

and adults with IDD.

4. The representativeness of national surveillance systems will improve if they consistently 

include people residing in the U.S. territories. 

 
Identifying People with IDD in National Surveys

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I. Introduction 

People with IDD are an important group to identify for government programs and public policy;

having an accurate prevalence estimate is important for planning. People with IDD receive 

significant public and private expenditures intended to support their well-being. Long-term 

supports and services (LTSS), including both institutional and home and community-based 

services (HCBS), accounted for 30% of all Medicaid expenditures in 2016, with 28% of all 

Medicaid-funded supports going to people with IDD (Eiken, Sredl, Burwell, & Amos, 2018).

People with IDD also comprise 14% of all working-age Supplemental Security Income and Social 

Security Disability Insurance beneficiaries (Livermore, 2017).

Public health and policy planning are compromised by the lack of national data on IDD

prevalence and the health status of people with IDD. Health surveillance data are essential to

allow population health researchers to track the incidence and prevalence of specific populations

and to identify characteristics that can influence or contribute to their health (Fox, Bonardi, &

Krahn, 2015). Accurate and timely data are critical for federal and state agencies to make

projections, establish policies, and implement programs to serve this population. The need for 

improved health surveillance data for people with IDD has long been recognized. For example, 

the Surgeon General’s report, Closing the Gap: A National Blueprint to Improve the Health of 

Persons with Mental Retardation (U.S. Department of Health and Human Services, 2002),

articulated the clear need to improve health surveillance for people with ID. 

A. Estimating the prevalence of IDD 

Prevalence estimates of IDD vary based on the operational definitions used and the purposes for 

data collection. Previous research in the U.S. has reported a prevalence of ID in children of 0.71% 

to 1.36% (Boyle et al, 2011; Braun et al, 2015), and for ID and/or DD of 1.9% (Larson, Doljanac, & 

Lakin, 2015 cited in Larson et al 2017). These estimates reach 16.24% when learning disabilities 

and attention deficit hyperactivity disorder are included in the definition (Boyle et al, 2011). Data 

from the NHIS-D (1994-1995) indicate the prevalence of IDD in adults to be 0.79% (Larson et al, 
Identifying People with IDD in National Surveys

14

2001) to 1.27% (Fujiura & Taylor, 2003), depending on operational definitions used. In the study 

by Larson and colleagues (2001), the combined prevalence estimates for ID, DD or both in the US 

non-institutionalized population were 38.2 per 1,000 for children birth to age 5, 31.7 per 1,000 

for children ages 6 to 17 years, 7.9 per 1,000 for adults, 14.9 per 1,000 for people of all ages 

(Larson, et al., 2001). The estimate increased to 15.8 per 1,000 for people of all ages when 

people with IDD in congregate residential settings were included. The prevalence estimates of 

IDD among children are typically higher than among adults, likely because of differences in 

definition, severity of disability, and differences in environmental demands that highlight 

limitations in some contexts, such as school. In addition, many prevalence studies of DD in 

children focus on categorical diagnoses such as ASD, or CP rather than on DD as defined by 

multiple functional limitations (e.g., Boyle et al., 2011; Braun et al., 2015).

Administrative prevalence of IDD can be estimated from data sources including Medicaid 

administrative claims (ICD 9 and 10 codes), the Medicare Current Beneficiary Survey, National 

Beneficiary Survey, NCES at the U.S. Department of Education, and Social Security Administration 

data sets. The characteristics of some individuals with IDD who receive state-level services can 

be examined through quality assurance programs such as the Medicaid Home and Community 

Based Services Consumer Assessment of Healthcare Providers and Systems (CAHPS) survey

(CAHPS Home and Community Based Services Survey), and the National Core Indicators (NCI). 

Administrative data are typically collected to describe recipients of service programs; however, 

such data sets provide incomplete and potentially misleading information for the purposes of 

estimating prevalence of IDD and measuring health disparities or unmet needs. For example, a 

prevalence estimate of 7.37 million people with IDD was obtained for 2016 using prevalence 

estimates based on the 1994-1995 NHIS-D, combined with the 2016 census data and estimates 

of people in congregate settings. However, only 20% of these people with IDD received services 

through state-level DD programs (Larson et al, 2018). This discrepancy indicates that 

administrative data, when collected, only captures a fraction of all people with IDD. It should be 

noted that while administrative data on IDD are currently collected by all states, the District of 
Identifying People with IDD in National Surveys

15

Columbia, and Puerto Rico, they are not collected by the other U.S. territories, making such

administrative data sets inadequate to estimate prevalence of IDD in all the U.S. states and 

territories. 

B. Impetus for this report 

Recognizing the need to establish better surveillance methods led AIDD to convene a multiagency, multi-stakeholder meeting in November of 2017 to explore issues and possible remedies 

for this information gap.

Participants included representatives from the following HHS federal agencies:

• Administration on Community Living (ACL)

• Centers for Disease Control and Prevention (CDC) 

• Assistant Secretary for Planning and Evaluation (ASPE)

• Centers for Medicare & Medicaid Services (CMS)

• Office on Minority Health (HHS)

and national disability organizations:

• Association of University Centers on Disabilities (AUCD)

• Center for Epidemiological Research for Individuals with Intellectual and Developmental 

Disabilities (CERIIDD)

• Human Services Research Institute (HSRI)

• National Association of Councils on Developmental Disabilities (NACDD)

• National Association of State Directors of Developmental Disabilities Services (NASDDS) 

The stakeholder meeting also included university-based researchers from nine different 

programs that focus on health surveillance and IDD. Subject matter experts from the following

universities and centers participated: Cincinnati Children’s Hospital Medical Center, Georgetown 

University, Ohio State University, Oregon State University, University of Illinois at Chicago, 

University of Colorado, University of Kansas, University of Minnesota, and University of New 

Hampshire. 
Identifying People with IDD in National Surveys

16

Through presentations and structured discussions, participants reviewed the status of health 

surveillance for people with IDD, available prevalence estimates, expected changes to data 

availability based on design changes to the NHIS, and strategies for improving health surveillance

for adults with IDD. AIDD and meeting participants agreed on the potential value of further 

investigation in two directions: (a) prevalence data from national surveillance and (b) richer 

contextual information from administrative data at the state, territory, and multi-state level. 

With an overarching goal to prioritize and address the need for better data to understand the 

prevalence, health status, and health determinants of people with IDD, two workgroups were 

formed. The specific charge for the AIDD National Health Surveillance Workgroup:

“(To collaborate with NCHS) to develop criteria/guiding principles and identify existing or 

draft additional (1-3) question(s) for use with the revised NHIS and other national surveys 

to identify persons with intellectual and developmental disabilities in order to determine 

prevalence of IDD (denominator).

 
Identifying People with IDD in National Surveys

17

II. Background 

 

A. Historical and legislative context in the U.S. 

While people with IDD have always been part of American society, advocacy efforts beginning in 

the early 1960’s brought increased national attention to their situations (Braddock & Parish, 

2001; Bersani & Lyman, 2009). Since that time, the understanding of IDD within the social 

context has continued to grow and change. Terminology has changed, diagnostic practices have

advanced, the nature of services and supports have continued to evolve, and technology has 

changed many aspects of life. Indeed, our very understanding of IDD has changed, along with 

increased societal expectations for richer, more participatory, and self-directed lives for people 

with IDD. For example, changes in our understanding and diagnosis of disabilities such as ASD

have influenced the prevalence of IDD in ways that are not yet fully understood. ASD was once 

thought to be a very rare condition; however, data from the 2014-2016 NHIS indicated ASD 

occurs in 24.7 children per 1,000 (Zablotsky et al, 2017). As the field of medicine has advanced, 

the development of effective medical interventions has reduced the impact of or even prevented

ID due to specific preventable causes such as iodine deficiency and phenylketonuria (World 

Health Organization, 1998).

The U.S. federal government has historically provided various sources of support for the IDD 

population. In 1965, the Medicaid program was introduced, offering federal funding through a 

partnership with states to provide services to certain low-income people, including some people 

with disabilities. Subsequently, Medicaid-funded Intermediate Care Facilities for Individuals with 

Intellectual Disability (ICF-ID, previously ICF/MR) facilities spurred state investments to reduce 

overcrowding and provide appropriate services to people with IDD in institutions. In 1981,

Congress passed a law that permits states to expand services in community-based settings 

through the use of Medicaid HCBS waivers. 
Identifying People with IDD in National Surveys

18

In addition to the Medicaid program, the federal government also provides educational services 

and supports for people with IDD. The Education for all Handicapped Children law 20 U.S,.C, §

1400 et seq, passed in 1975 guarantees a free and appropriate public education for all students 

regardless of the type or severity of their disability. The Rehabilitation Act of 1973 prohibits

discrimination against people with disability in federally-funded services. The Americans with 

Disabilities Act (ADA), passed in 1990, prohibits discrimination based on disability in all areas of 

public life. As the above legislation have been reauthorized and updated by Congress, and public 

policies changed to promote community living, there has been widespread downsizing or closure 

of publicly-funded institutions and a corresponding growth of community-based services for 

people with IDD. 

Also rooted in the U.S. social fabric are the cultural views and biases, both implicit and explicit,

regarding people with IDD (Scior, 2011; Werner, Corrigan, Ditchman & Sokol, 2012). Racial and 

ethnic biases in the U.S. have additionally impacted how people with IDD from minority 

backgrounds are diagnosed (Fish, 2002). Such biases are apparent in the overrepresentation, in 

special education programs, of African American children and Latino children with limited English 

proficiency. In addition, a complex array of dynamics further contributes to a pattern of 

disparities in health, education, and employment. These include, but are not limited to,

stereotyping, conscious and unconscious biases, culturally-biased assessment instruments and 

practices, institutional and structural racism, and the debilitating effects of living in marginalized 

and disadvantaged families and communities (Goode, Jones, Christopher, & Brown, 2017). These 

issues are targeted by current efforts to address health equity within HHS (OMH U.S. 

Department of Health and Human Services Office of Minority Health).

The majority of people with IDD live with their families and caregivers in their homes or in other 

home and community-based settings. There were an estimated 7.37 million adults and children 

with IDD in the U.S. in 2016 based on calculations using IDD prevalence rates from the 1994-95 

NHIS for adults, the 2016 NHIS for children, the 2016 U.S. Census, and data on people with IDD 

living in congregate settings in 2016 (Larson et al., 2018). In 2016, an estimated 1.49 million 
Identifying People with IDD in National Surveys

19

people with IDD (20% of the estimated 7.37 million IDD population) were known to state IDD 

agencies, and 1.23 million (17%) received Medicaid- or state-funded long term services and 

supports (LTSS) administered by state IDD agencies (Larson et al, 2018). Of those receiving 

funded supports, 58% lived with a family member, and most of the rest lived in a home or 

community-based setting shared by six or fewer people with IDD. While administrative data can 

be used to understand the characteristics and needs of current service recipients with IDD, data 

based on the U.S. noninstitutionalized population are needed to fully count the IDD population 

as well as understand their health status, health disparities, health outcomes, and residential 

circumstances.

B. Conceptualizations of disability 

The concept of disability has evolved over the past century (Iezzoni & Freedman, 2008), with 

changing conceptualizations reflected in changing definitions in federal statutes. During much of 

the 20th century, experts considered IDD within a medical model, which views disability as a 

health problem arising directly from disease, trauma, or medical condition, with the disability 

residing within (or as a trait of) the individual. The medical model’s perspective is that the 

person’s condition or difference results in the individual’s inability to function (Iezzoni & 

Freedman, 2008). The use of diagnostic categories to classify disabilities is founded in the 

medical model.

The independent living and civil rights movements, focused attention on those external forces as 

sources of limitations (such as social and environmental circumstances). The social model views 

disability as a condition resulting from the demands or expectations of the social environment, 

including how the society is organized, prejudice, physical and attitudinal barriers, and 

discrimination (Mont, 2007). The social model of disability views social policies as the solution to 

disability, in particular policies that direct change to environments, prevent discrimination and 

exclusion, and increase opportunities for participation. Influenced by this emphasis on a social 

model, a committee of the World Health Organization (WHO) worked for more than two 

decades to define disability in a framework that integrated these differing conceptualizations 
Identifying People with IDD in National Surveys

20

(Pope & Tarlov, 1991). The most recent version, the International Classification of Functioning, 

Disability and Health (ICF) (WHO, 2001), was endorsed by all 191 member states. The ICF 

presents a view of disability as “a complex phenomenon, reflecting an interaction between 

features of a person’s body and features of the society in which he or she lives,” and as such 

asserts that “[o]vercoming the difficulties faced by people with disabilities requires interventions 

to remove environmental and social barriers” (WHO, 2011). 

Changes in federal laws, both enacted by Congress and as interpreted by the U.S. Supreme 

court, have greatly impacted the concept of disability within the last 20 years. The Americans 

with Disabilities Act (ADA) was first passed in 1990 (42 USC § 12101 et seq.) and the ADA as 

Amended (42 USCA § 1201 et seq.) passed in 2008; both describe the purpose of the ADA to be a 

national mandate for the elimination of discrimination against individuals with disabilities (42 

USCA § 12101 2(b)(1)). The ADA defines disability as “a physical or mental impairment that 

substantially limits one or more major life activities of such individual,” “a record of such an 

impairment,” or “being regarded as having such an impairment.” As civil rights legislation, the 

ADA defines disability broadly to encompass physical and mental impairments and prohibits 

discrimination against people with disabilities. The ADA further established the civil rights of 

individuals with disabilities to full participation in society by mandating reasonable 

accommodations as a strategy to enable their full participation. In June 1999, the U.S. Supreme 

Court further clarified the ADA in its decision in Olmstead v. L.C., 527 U.S. 581, concerning the 

right of people to live and participate in community-based settings.

 

C. Defining intellectual and developmental disabilities 

As documented by the Interagency Committee on Disability Research (ICDR), definitions of 

disability and the criteria used to meet disability determinations vary widely across federal 

agencies, particularly among those definitions related to program eligibility (CESSI, 2009). In 

general, the definitions used for ID and DD are consistent with professional practice and federal 
Identifying People with IDD in National Surveys

21

legislation as contained within the DD Act. Because these definitions require significant 

functional limitations, they exclude some people who are not severely limited by their condition.

The DD Act had its origins in 1961, which in turn contributed to the Maternal and Child Health 

and Mental Retardation Planning Amendments of 1963 and the Mental Retardation Facilities and 

Community Mental Health Centers Construction Act of 1963. In subsequent years, legislation 

and definitions were updated as society’s understanding of IDD changed.

In passing the latest iteration of the DD Act, Congress acknowledged the significance of the 

concept of function and full participation in society when it noted in its finding that:

“. . disability is a natural part of the human experience that does not diminish the 

right of individuals with DD to live independently, to exert control and choice over 

their own lives, and to fully participate in and contribute to their communities 

through full integration and inclusion in the economic, political, social, cultural, and 

educational mainstream of United States society” (emphasis added). 42 U.S.C.

§15001(a)(1).

i. Developmental Disabilities 

This paper uses the definition of DD promulgated in the DD Act o (42 U.S.C. §15001 et seq.), that 

is,

“a severe, chronic disability that is attributable to a mental or physical impairment, is 

manifested before the individual attains age 22, is likely to continue indefinitely, 

results in substantial functional limitations in three or more of the following areas of 

major life activity: self-care; receptive or expressive language; learning; mobility; selfdirection; capacity for independent living; and economic self-sufficiency; and reflects 

the individual’s need for a combination and sequence of services and supports.”

Children from birth through the age of 9 years old with significant developmental 

delays and specific congenital or acquired conditions do not need to meet the 

functional limitations criteria to be considered to have DD.”
Identifying People with IDD in National Surveys

22

ii. Intellectual Disability 

While ID is not defined in federal statute, the U.S. Supreme Court and federal entities such as 

ACL and the President’s Committee for People with Intellectual Disabilities (PCPID) within HHS 

recognize the American Association on Intellectual and Developmental Disabilities’ (AAIDD) 

definition of ID as “a disability characterized by significant limitations in both intellectual 

functioning and in adaptive behavior, which originates before the age of 18” (Schalock et al, 

2010). Intellectual functioning, or intelligence, refers to general mental ability including 

reasoning, planning, problem solving, thinking abstractly, comprehending complex ideas, 

learning quickly, and learning from experience. Significant limitations in intellectual functioning is 

operationally defined as an IQ score that is approximately two standard deviations below the 

mean (Schalock et al, 2010). As one standard deviation is 15 points below the mean of 100 for 

most standardized intelligence tests, two standard deviations below the mean would be an IQ 

score of approximately 70.

Adaptive behavior is the collection of conceptual, social, and practical skills that have been 

learned and are performed by people in their everyday lives (Schalock et al, 2010). Conceptual 

skills include language, reading and writing, time, and number concepts. Social skills refer to 

interpersonal skills such as social responsibility, self-esteem, gullibility, following rules/obeying

laws, and social problem solving. Practical skills are activities of daily living (personal care), 

occupational skills, use of money, safety, health care, travel/transportation, schedules/routines, 

and use of the telephone. For the diagnosis of ID, significant limitations in adaptive behavior are 

operationally defined as performance that is approximately two standard deviations below the 

mean of either (a) one of the three types of adaptive behavior (conceptual, social, or practical),

or (b) an overall score on a standardized measure of conceptual, social, and practical skills. 

The term used to refer to people with ID has evolved over time as older terms (most recently

mental retardation) acquired negative connotations and became offensive to many people. In 
Identifying People with IDD in National Surveys

23

2010, with the passage of Rosa’s Law (Pub. L. 111-256), references to “mental retardation” in 

federal laws were replaced with the term intellectual disability. This legislation substituted one 

term for another, but did not change eligibility determination or programming.

iii. Comparing ID with DD 

While ID is typically regarded as one type of DD, the two conditions do not overlap perfectly

when the definition of DD is based on the DD Act. If a person with ID does not experience 

substantial limitations in three or more specified life activities, they will not meet criteria for DD 

as outlined in the DD Act. Larson et al. (2001) analyzed the NHIS-D (1994/95) data to compare 

survey members who met criteria for ID, for DD, and both. Among adults, 40% of individuals with 

IDD were identified as having both ID and DD, 26% were identified as having ID but not DD 

because they had significant limitations in only two areas of major life activities (intellectual 

functioning/learning and one type of adaptive behavior) but not three or more, and 34% were 

identified as having DD but not ID because learning was not one of their three substantial 

functional limitations (See Figure 1).

 

Figure 1. Adults in the NHIS-D with Intellectual Disability, Developmental Disabilities, or Both. 

 Data Source: Larson et al., 2001

Appendix A provides an overview of the domains of ID and DD as defined by the DD Act.

 

ID no DD

26%

DD no ID

34%

ID and DD 

40%
Identifying People with IDD in National Surveys

24

D. Past approaches to measuring IDD 

i. Function vs. Diagnosis 

Data collection about people with IDD varies greatly, and may utilize either diagnostic conditions,

functional limitations, or both. For example, many health care services, medical care 

reimbursement, and rehabilitation research are based on diagnostic conditions. The Social 

Security Administration relies on detailed medical diagnoses as its first step in determining 

eligibility for its entitlement programs, followed by determination of one’s ability to work 

(Livermore, Bardos, & Katz, 2017). Alternatively, the Maternal and Child Health Bureau (MCHB) 

made a distinct change in its basis for service eligibility from diagnostic categories to a more 

functional model to identify “children with special health care needs” (HRSA, n.d.). Data from the 

Department of Education’s special education services reflects a combination of diagnostic 

categories and severity of functional impairment (National Center for Education Statistics, n.d.). 

In the absence of a cohesive approach in conceptualization and measurement of ID and DD, this 

remains a challenge for interoperability across federal agencies.

The umbrella concepts of substantial impairments in intellectual functioning, adaptive behavior, 

and major life activities emphasize a multidimensional view of IDD. However, the construction of 

survey questions to identify people with IDD largely reflects narrower views of disability that 

emphasize either the condition of the person or the consequences of a condition. This approach 

is usually operationalized as a question about the presence of a condition (“Does ____ have an 

intellectual disability?”) or limitations in specific functions, life activities, or need for supports 

(“Does ____ have difficulty learning or engaging in activities typical for their age?”). In order to 

identify people with IDD, questions about limitations in function or activities are sometimes 

enhanced by subsequent questions about causation (e.g., “What condition is the cause of the 

limitation?”).

 
Identifying People with IDD in National Surveys

25

ii. Single Questions or Multiple Question-Sets 

Of the few recurring population-based or administrative data systems that screen for ID or DD, 

most employ a single item about the presence of ID or DD as a condition (Bonardi et al, 2011). 

Notable exceptions, prior to their redesign, were the NHIS and SIPP; however, capturing the 

nature of a multidimensional view of IDD typically requires more than a single question that 

indicates inclusion or exclusion from a group. The reliability and validity of survey-based IDD 

identification improves as the number of questions increases. For example, IDD identification 

using a condition-based screen (“Do you have IDD?”) versus a cause of limitation question (“Is 

IDD the primary cause of the limitation?”) in the NHIS and SIPP resulted in overlapping but not 

totally congruent samples. Further, when using a single question on the cause of limitation as ID

in the 2000 NHIS, and comparing this with the combination of questions available to identify 

mental retardation [sic] in the 1994-95 NHIS-D, Hendershot, et al (2005) identified only one-third 

the size of estimated people with ID. The optimal number of questions, and their content and 

wording are yet to be determined, but it is clear that more questions will provide more precision 

and multidimensionality.

iii. Self-and Proxy-Reporting 

 

A further challenge for survey construction is the reliance on inter-changeable self- and proxyreporting. In the 2001-2002 NHIS Adult Survey, proxy responses were used for 59.3% of adults 

with ID versus 1.2% of all adults (Hendershot, 2004). Research examining concordance between 

self-report and proxy-report has highlighted that (a) knowledge of the person by the proxy and 

(b) the nature of the construct measured are important in determining degree of agreement 

(e.g., Schmidt et al, 2010; Claes et al, 2012). Specifically, close family members’ proxy-responses 

are more aligned with self-report than professional report; and questions related to internal 

experiences are at greater risk of discordance. Finally, whether by self- or proxy-report, stigma 

and related reluctance to disclose limitations in intellectual and developmental functioning are 

suspected to contribute to under-reporting. 
Identifying People with IDD in National Surveys

26

III. Surveillance Gaps and Strategies for Identifying IDD Respondents in 

Population-Based Surveys 

 

To address its charge, the workgroup sought to investigate and answer several key questions:

a) Do recently adopted standard question sets on disability enable identification of people 

with IDD?

b) Are data available for adults with IDD as well as children with IDD?

c) What content domains are present in the revised NHIS 2019 survey and what additional 

domains are needed for identification of people with IDD?

d) What existing questions are available from other surveys in needed content domains?

e) What additional methodological considerations are needed?

A. Limitations of current disability identification questions 

Past efforts to establish a unified framework for disability statistics led a number of federal data 

collection efforts to include a standard set of questions on functional limitations in basic and

universal domains of activity (e.g., seeing, hearing, mobility, cognition, and self-care).

The development of the ACS disability question set, a set of six questions that ask about difficulty 

with seeing, hearing, mobility, cognition, self-care and independent living using a yes/no 

response (United States Census Bureau) (U.S. Census Bureau), has enabled people with 

disabilities to be identified in several U.S. population-based surveys (e.g., ACS, CPS, SIPP); 

however, it is not possible to identify people with IDD using this question set.

The NHIS uses a slightly different set of six disability identification questions: the international 

standard, known as the Washington Group Short Set (WG-SS) (Madans, Loeb, & Altman, 2011). 

The WG-SS captures information on difficulty with seeing, hearing, mobility, cognition, self-care 

and communication using a continuum of response options in order to capture severity (The 

Washington Group Short Set of Questions on Disability). One functional domain common to both 

question sets is cognition. An ACS question asks about “serious difficulty concentrating, 

remembering, or making decisions,” while the analogous WG-SS question asks about “difficulty 
Identifying People with IDD in National Surveys

27

concentrating or remembering.” People who report this type of difficulty have a wide array of 

conditions, including dementias such as Alzheimer’s disease, stroke and traumatic brain injury, 

schizophrenia or other mental health conditions, and health conditions requiring medications 

that affect cognition. Unfortunately, a single question on cognition does not provide sufficient 

information to differentiate between people with IDD and those with other conditions.

B. Available survey data for adults and children with IDD 

i. Adults with IDD in the U.S. 

Only three peer-reviewed studies using the NHIS-D data published since 2000 report prevalence 

of ID and/or DD in U.S. adults, and none of these were published after 2015. One study using 

NHIS-D (1994-95) data reported an adult prevalence rate of 7.8 per 1,000 for ID, DD or both and 

an all-age prevalence rate of 14.9 per 1,000 (Larson et al, 2001). A second study with NHIS-D 

(1994-95) data estimated the prevalence of ID, including mild intellectual impairments

(impairments not severe enough to meet the AAIDD threshold), to be 12.7 per 1,000 (Fujiura & 

Taylor, 2003). A study using the 2008-2012 SIPP data estimated the prevalence of IDD for 

children and adults 6 years or older to be 10.3 per 1,000 (Burke & Fujiura, 2013). International 

estimates for adults with ID across a range of countries and data sets are approximately 10.37

per 1,000 (Maulik, Mascarenhas, Mathers, Dua, & Saxena, 2011; McKenzie, Milton, Smith, & 

Ouellette-Kuntz, 2016), with Western Australia using multiple data sources reporting prevalence 

as 17.0 per 1,000 (Bourke, et al, 2016).

Only two peer-reviewed studies are available which analyzed prevalence rates of IDD in U.S. 

adults by race and ethnicity. Using ten years of linked NHIS and Medical Expenditure Panel 

Survey (MEPS) data (2002-2011), Fujiura, Li, and Magaña (2018) found higher rates of IDD 

among Black Americans (14 per 1,000) and nearly identical rates among White (9 per 1,000) and 

Hispanic Americans (8.2 per 1,000). An earlier study (Fujiura & Yamaki, 1997) reported a similar 

pattern for prevalence by race and ethnicity using 1990-1991 SIPP panels for children and adults 

aged 3 and older. 
Identifying People with IDD in National Surveys

28

A Native American developmental disabilities needs assessment published in 2012 revealed that 

there are no national IDD prevalence data specific to the American Indian/Alaska Native 

populations (AI/AN). The AI/AN populations have the highest rate of general disability in the U.S.,

with 27% of working age adults and 7.7% of children having a disability. For comparison, the 

rates of general disability for non-Hispanic white are 16.2% for adults and 5.7% for children 

(Cohen, et al 2012).

An entire generation of children with severe lifelong disabilities finished school and transitioned 

into adulthood since the 1994-1995 NHIS-D was fielded. Aside from the National Longitudinal 

Transition Study 2, which followed recipients of special education who were in 7th grade or 

above in 2000 for up to eight years after graduation (Newman et al., 2011), very little is known 

about the noninstitutionalized adult population with ID and DD. 

ii. Children with IDD in the U.S. 

Unlike the paucity of studies about adults, children with ID and DD are identifiable in several 

ongoing public health surveillance efforts. Between 2000 and 2018, at least 35 studies were 

published reporting prevalence rates for ID and DD in children. A study using the 2011-2013 

NSCH estimated that the prevalence of ID in children 3 to17 years old was 1.26% (Maenner, et 

al., 2016). A study using the 2014 NHIS estimated prevalence rates for children ages 3 to 17 

years of 1.14% for ID, 2.76% for ASD, 4.55% for other developmental delays and 6.99% for one or 

more of these conditions (Zablotsky, Black, Maenner, Schieve, & Blumberg, 2015). The 

prevalence of ID, DD, ASD, and Down syndrome in children has increased dramatically since 

1995. It is unknown how much of this measured increase relates to increases in awareness, 

changes in definition, increased longevity, changes in prevalence or other factors. 

The number of people in the US with Down syndrome quadrupled from 49,923 in 1950 to 

206,366 in 2010 (de Graaf, Buckley, & Skotko, 2017) while the country’s overall population size 

doubled from 152.3 million to 309.3 million during that same time. The proportion of children 
Identifying People with IDD in National Surveys

29

aged 6 to 17 years receiving special education in 2017 was 0.73% for ID, 1.03% for ASD, 0.22% 

for multiple disabilities, and 0.26% for developmental delay (2.45% for the four categories 

combined) (EDFacts Data Warehouse, 2017; NCES, 2017). While studies from the 1990’s showed 

substantially higher prevalence estimates for children compared with adults, little is known 

about whether this continues to be true today.

Several studies have documented differences in IDD prevalence rates in U.S. children across race 

and ethnicity. An analysis of NHIS data from 1997-2008 (Boyle, et al, 2011; Blumberg, 2012) 

revealed that compared to White children, Black children were 1.7 times more likely to be 

identified with ID and equally likely to have DD, while Hispanic children were significantly less 

likely than White children to be identified to have DD (odds ratio [OR] = .7) and equally likely to 

have ID (OR = 1.1). While there are no prevalence estimates for IDD among AI/AN children, of 

the AI/AN children in tribal-operated schools or schools that are operated by the Federal Bureau 

of Indian Education, 21% were in special education compared to 13% of all U.S. public school

students (Cohen, et al, 2012).

The workgroup considered the data available for children and adults in the current NHIS and 

other national surveys. While data to identify children with IDD were considered generally 

adequate, significant concerns were raised around the need for current data on adults. The 

workgroup strongly recommended that there be a priority on including questions for 

identification of adults with IDD in national surveys.

 

C. Domains required to identify ID and DD 

 

i. Domains Required by the Definitions of ID and DD 

Using the DD Act definition for DD and the AAIDD definition for ID, the workgroup first reviewed

current population survey programs that measure some or all of the domains needed to identify 

sample members with IDD. The workgroup also identified domains not currently included in U.S. 
Identifying People with IDD in National Surveys

30

population-based surveys that are needed to identify people with IDD. The 2016 NHIS survey 

(before the current redesign) included items covering limitations in five of the seven DD Act 

major life activity areas (communication, self-care, capacity for independent living, economic 

self-sufficiency, and mobility), but did not include items to assess limitations in learning, selfdirection, age of onset, or expected duration of limitations. Table B1 in Appendix B lists the 2016 

NHIS items in these five areas by subscale. 

Table 1 below describes the essential domains for identifying ID and DD and their presence or 

absence in the 2019 NHIS. These domains are derived from the AAIDD definition of ID and the 

DD Act definition of DD. 

 

Table 1. Essential domains to identify ID and DD. 

Major life activity domain Intellectual 

Disability 

Developmental 

Disabilities 

Construct 

captured in 

redesigned NHIS 

Intellectual functioning √

Adaptive Behavior

 Conceptual skills

Learning (academics) √ √

Self-direction √

 Practical skills

Self-care √ √ √

Independent living skills √ √

Economic self-sufficiency √ √ √

 Social skills

Communication √ √ √

Mobility √ √

Other criteria Intellectual 

Disability

Developmental 

Disabilities

Construct 

captured in 

redesigned NHIS

Age of onset √

(Before age 18)

√

(Before age 22)

Severity √ √ √

Lifelong duration √
Identifying People with IDD in National Surveys

31

While the essential domains for ID and DD certainly overlap, it is clear that adaptive behavior 

constructs named in the ID definition were broader in scope. For example, significant deficits in 

practical skills is one element of the ID definition. Although practical skills are not mentioned by 

name in the DD Act, the discrete components of practical skills including self-care, independent 

living skills, and economic self-sufficiency are essential major life activity domains in the DD Act. 

Table 1 provides a list of essential skills and abilities to identify ID and DD where discrete skills 

are indented under the conceptual domains. Check marks indicate the elements that are 

essential to a diagnosis of ID or DD and the final column indicates whether or not the construct is 

measured in the 2019 NHIS. One point of discussion among committee members had to do with 

the lifelong duration criterion. While the AAIDD definition of ID certainly conceptualized ID as a 

lifelong condition, duration was not named nor is it assessed to establish a diagnosis of ID. In 

contrast, the DD Act explicitly named lifelong duration as a criterion. Therefore, lifelong duration 

is checked as essential for DD and not ID in Table 1.

The redesigned 2019 NHIS measures some of the domains needed to identify people with IDD, 

specifically mobility, communication, self-care, and economic self-sufficiency. In addition, the 

2019 NHIS includes items on social participation which, while not currently a DD Act criterion, 

could be considered for addition in future DD Act reauthorizations based on current 

understanding of the importance of social participation to health and human function. Criteria 

for the DD Act definition of DD which are not included in the 2019 NHIS are the domains of

learning, independent living, and self-direction, as well as age of onset (before 22 years), and 

projected duration of the limitation (lifelong or extended duration). Criteria for the AAIDD 

definition of ID that are not addressed in the 2019 NHIS are the domains of intellectual 

functioning, conceptual skills, social skills, and age of onset (before age 18). Elements needed to 

identify DD that are missing from the 2019 NHIS include independent living skills, self-direction, 

and age of onset (before age 22). In summary, the 2019 NHIS does not address intellectual 
Identifying People with IDD in National Surveys

32

functioning, conceptual skills, social skills, independent living skills, self-direction, age of onset, or 

projected duration of the limitation.

 

ii. Domains that Best Predict IDD Status 

When data from the NHIS-D (1994-95) were analyzed to identify the items that best discriminate 

between survey participants who had IDD and those who had functional limitations but not IDD, 

differentiating characteristics could be identified (Doljanac, Larson, & Lakin; 2004). Figure 2 

shows the domains that contributed to the identification of adults with IDD. In a series of logistic 

regression analyses, once sex, age, health status, race, and economic status were considered, 

adults who met criteria for ID or DD were more likely than adults with other functional 

limitations to have significant functional limitations in learning (OR =46.85), economic selfsufficiency (OR = 8.38), communicating with family (OR = 8.64) or with non-family (OR = 8.04), 

self-direction (OR = 6.01), difficulties understanding others (OR = 5.09), and personal care (OR = 

2.90). These findings further informed the workgroup’s item development considerations.

 

Figure 2. Proportion of adults with IDD and adults with other functional limitations across areas 

of function (NHIS-D 1994-1995). 
Identifying People with IDD in National Surveys

33

Based on the above findings, the workgroup identified the following priority areas to consider for 

item development and testing for future national surveys, in addition to those in Table 1: 

• Learning

• Independent Living

• Age of Onset

 

D. Questions from other surveys that assess needed domains 

Because the current NHIS does not include a sufficient range of items to identify the IDD 

population, the workgroup examined former population survey questions as potential sources of 

questions to identify adults with IDD for future NHIS and other national surveys.

i. Survey of Income and Program Participation (1984-2013) 

The SIPP is a national survey program of the non-institutionalized civilian population in the U.S. 

including Puerto Rico, begun in 1984 and conducted annually by the U.S. Census Bureau. The 

30

13

13

62

15

11

45

11

14

30

46

50

88

88

0 10 20 30 40 50 60 70 80 90 100

Mobility

Personal Care

Language

Independent Living

Self-Direction

Learning

Economic Self-sufficiency

Proportion of Adults with IDD or Other Functional 

Limitations who had Limitions in each DD Act 

Category

ID, DD or Both Functional Limitations No IDD
Identifying People with IDD in National Surveys

34

2008-2013 SIPP was notable for its extensive disability and function modules, which included 

more than 90 questions focused on health status, activity and functional limitations, activities of 

daily living (ADLs) and Instrumental Activities of Daily Living (IADLs), the presence of specific 

impairments and medical conditions, age of onset and duration, need for assistance, and 

conditions that were considered the primary reason for limitations. There were separate items 

for adults, children, and very young children. The 2008-13 Panel was the final implementation of 

an extended disability topical module. With the 2014 redesign of the SIPP, a smaller set of 

disability questions was used that focused solely on functioning rather than type of impairment, 

and as a result people with IDD cannot be identified.

The general approach and question structure of the disability module from the SIPP may be 

informative for future IDD survey question development. Appendix B, tables B1 and B2, 

summarize items used to identify adults and children with IDD, respectively. Two groups of items 

from the 2008-2013 SIPP are represented. For the first group of items, if a respondent 

acknowledged a limitation or difficulty, he or she was asked to identify from a list the condition 

or conditions that caused the difficulties. Mental retardation [sic]and cognitive impairment 

[learning disability] were options). The second group of IDD screening questions was a direct 

query asking the respondent if they had mental retardation [sic]or a developmental disability or 

related condition. The analyst could base identification on respondent or proxy identification as 

having ID, DD, or other combinations, as well as include functional and activity limitation 

conditions in the identification. 

ii. National Health Interview Survey - Disability Survey (1994-1995) 

The NHIS-D was a one-time supplement to the NHIS. Prompted by awareness of the need for 

better policy-relevant data on disabilities, 11 federal agencies—along with the Robert Wood 

Johnson Foundation—collaboratively planned and funded the NHIS-D which was conducted in 

two phases in 1994 and 1995. In the NHIS-D, adults were identified as having DD if they had 

substantial functional limitations in at least three of the seven DD Act areas (self-care, 
Identifying People with IDD in National Surveys

35

communication, learning, mobility, self-direction, independent living, and economic selfsufficiency), the difficulty began before age 22, and the limitation was expected to continue for 

at least 12 more months (See Table B2 in Appendix B for more details). Adults could be identified 

as having ID if they reported having (a) mental retardation[sic], (b) an ICD code (i) indicating ID as 

a cause of limitations in learning, communication, getting along with others, activities of daily 

living, instrumental activities of daily living, or work, or (ii) listing the condition as a reason for a 

health care visit, or (c) having a learning disability AND a related condition such as CP, Down 

syndrome, spina bifida, autism, or hydrocephalus AND had completed no more than 14 years of 

education (2 years of post-secondary education). 

 
Identifying People with IDD in National Surveys

36

iii. Essential Domains to Identify IDD for Health Surveillance 

a. Learning 

The workgroup concluded that without survey items to capture intellectual functioning or 

functional limitation in learning, it will not be possible to identify adult sample members with 

IDD. The workgroup identified several items used for leaning in other surveys that could be 

tested for this purpose in the table below. It is noted that several of the items used in other 

surveys are diagnosis-based. 

Table 2. Learning questions from other surveys. 

Survey Questions 

NHIS-Child (2012) Ever told by doctor or other health professional that you have an 

intellectual disability?

NHIS-Child (2012) Ever told by doctor or other health professional that you have autism 

spectrum disorder? 

NHIS-Child (2012) Ever told by doctor or other health professional that you have another 

developmental disability?

SIPP (2008-2013) (1) Does _____________ have (a) A learning disability such as 

dyslexia? (b) Mental retardation? (c) A developmental disability such 

as autism or cerebral palsy?

NHIS-D (1994-1995) ______________ has serious difficulty learning how to do things most 

people their age can learn?

WHODAS 2.0 (2010) In the last 30 days how much difficulty did you have in:

• Analyzing and finding solutions to problems in everyday life

• Learning a new task, for example, learning how to get to a new 

place

Ohio Medicaid 

Assessment Survey

(2017)

Do you have a developmental disability?

Diagnostic Adaptive 

Behavior Scale

(DABS) (2017)

If you attended school, did you receive special education?

Diagnostic Adaptive 

Behavior Scale

(DABS) (2017)

Did you have significant difficulties learning in school or to read or 

write?

 

 
Identifying People with IDD in National Surveys

37

b. Independent Living Skills 

Independent living skills are an essential construct in the definitions of ID and DD, yet this 

domain is not addressed in current population surveys. The following items used to measure 

independent living may inform item development.

Table 3. Independent living questions from other surveys.

Survey Questions 

American 

Community Survey 

(2017)

Because of a physical, mental, or emotional condition, does this person 

have difficulty doing errands alone such as visiting a doctor’s office or 

shopping?

Health and 

Retirement Study

(2016)

Because of a health (or memory) problem do you have any difficulty with 

• Dressing, including putting on shoes and socks?

• Bathing or showering?

• Eating, such as cutting up your food?

• Getting in or out of bed?

• Using the toilet, including getting up and down?

• Using a map to figure out how to get around in a strange place?

• Prepare hot meals?

• Shopping for groceries?

• Making phone calls?

• Taking medications?

• Managing your money -- such as paying your bills and keeping 

track of expenses?

Health and 

Retirement Study

(2016)

Did anyone help by supervising [him/her] to ensure safety, provide 

reassurance, or to make sure that nothing went wrong?

Health and 

Retirement Study

(2016)

Do you get any help with work around the house or yard because of a 

health problem?

NHIS-D (1994-

1995)

Do you need help from another person for the following activities or 

does someone else always do this for you because you cannot (each 

activity asked as its own question)

● Preparing meals

● House cleaning

● Handling money

● Shopping for yourself

● Medication management 

● Going somewhere/independently accessing transportation 

● Being home alone for 2 or more hours
Identifying People with IDD in National Surveys

38

c. Age of Onset 

Both ID and DD are conceptualized as lifelong conditions that are first apparent during the 

developmental period; however, the AAIDD definition of ID operationalizes this onset as before 

the age of 18 while the DD Act operationalizes this onset as before the age of 22. The redesigned

NHIS does not assess whether specific limitations were apparent during the developmental 

period nor does it assess the expected duration of particular limitations. The workgroup 

discussed several possible strategies to assess age of onset and expected duration in national 

surveys, and determined that, given survey constraints, it would not be necessary to ask about 

age at onset for every functional limitation item. Rather, when a respondent indicates that they 

have a substantial limitation (e.g., have a lot of difficulty or are unable to do) in any of the 

qualifying conditions or limitations, a single follow up question should be asked to determine if 

the limitation first occurred before the person was 22 years old. 

iv. Additional Domains Needed for IDD Prevalence Estimates 

In its deliberations, the workgroup identified areas to consider for future item development that 

might be added to the NHIS or other national surveys. These areas are not comprehensive, but 

arose in the workgroup’s discussion of item sets that could inform prevalence research. In 

addition to the minimum item set (learning, independent living, and age of onset), major life 

activity domains to consider for future item development include: 

a. Communication 

Functional limitations in communication is a domain specified in the DD Act, and communication 

is a type of adaptive behavior under the AAIDD definition of ID. The 2016 NHIS included only one 

item on difficulty communicating. The following items to measure communication are provided 

in the figure on the next page. 

 
Identifying People with IDD in National Surveys

39

Table 4. Communication questions from other surveys. 

Survey Questions 

WG-SS (2002) Using your usual (customary) language, do you have difficulty 

communicating, for example understanding or being understood?

NHIS-D (1994-

1995)

Because of a physical, mental or emotional problem, the person has a lot 

of difficulty or is unable to use a telephone

NHIS-D (1994-

1995)

Person has serious difficulty communicating with people outside of the 

family.

NHIS-D (1994-

1995)

Person has serious difficulty understanding others when they talk or ask 

questions.

WHODAS 2.0

(2010)

In the last 30 days how much difficulty did you have in:

• Generally understanding what people say

• Starting and maintaining a conversation

 

b. Self-Direction 

The health surveillance intent of identifying survey respondents with limitations in autonomous 

decision-making, in conjunction with other data, would be to better estimate the prevalence of 

people with DD. A review of the literature on self-direction and self-determination was 

conducted to explore possible survey items to measure self-direction. The workgroup used “selfdirection” to refer primarily to personal capacity or functional ability to make their own free 

choices, consistent with the construct of major life activities outlined in the DD Act. “Selfdetermination,” on the other hand, was used in the DD Act to refer to control over those 

activities and environmental supports that offer opportunities to communicate choices and 

exercise control over their lives (DD Act). As noted by Mumbardo-Adam and colleagues (2017), 

self-determination requires “both personal capacities and environmental opportunities” 

(Mumbardo-Adam, et al, 2017). 

Despite great efforts, the workgroup identified little literature to inform this issue. Indeed, the 

workgroup concluded that it is difficult to conceptualize the ability to make choices apart from 

the ability to understand and/or communicate choices, and the ability to self-direct also 

depends, to a large degree, on having the opportunity to exercise choices. 
Identifying People with IDD in National Surveys

40

CMS uses “self-direction” to indicate that HCBS recipients or their representatives have decisionmaking authority over certain services and responsibility to manage them with the assistance of 

a system of available supports (CMS, n.d.). Such a model is an alternative to traditionally 

delivered and managed services, such as an agency delivery model. Most Medicaid self-directed 

programs allow states to convey employer authority and budget authority to Medicaid 

beneficiaries, often in the provision of personal care and other HCBS services. Employer 

authority permits Medicaid beneficiaries to manage their own direct service staff in terms of 

determining the requisite skills and training, and to hire, fire, and supervise staff. Budget 

authority permits beneficiaries to allocate their HCBS budget, which could include setting the 

hourly wages for their staff. Fiscal intermediaries may be used to ensure accounting for their 

worker’s wages, benefits, and other items within the budget. 

Medicaid and other publicly-funded LTSS programs use a variety of tools to assess the extent to 

which their beneficiaries are receiving services that support self-determination. Tools currently 

available for this purpose include HCBS CAHPS survey, the Council on Quality and Leadership’s 

Personal Outcome Measures, and the National Association of State Directors of Developmental 

Disabilities Services’ (NASDDDS) NCI. 

For the current purposes, however, the goal is not to assess whether people receive services 

supportive of self-determination, nor is the goal to examine any specific Medicaid service 

delivery models. Rather, the workgroup considered what survey items could be used to identify 

people with limitations in autonomous decision-making. In light of the difficulty in isolating items 

to measure self-direction (and disentangling it from the opportunity to exercise choice), the 

workgroup concluded that additional conceptual work was needed on the construct. The 

following items were used in NHIS-D to measure self-direction; however, they do not disentangle 

ability from opportunity.

 

 
Identifying People with IDD in National Surveys

41

Table 5. Self-direction questions from other surveys. 

Survey Questions 

NHIS-D (1994-

1995)

Because of a physical, mental or emotional problem the person needs to 

be reminded or have someone close by for

• Eating

• Bathing

• Dressing

• Using a toilet

• Transferring in and out of bed

NHIS-D (1994-

1995)

Do you have a court appointed representative currently authorized to 

make decisions on your behalf such as a guardian, conservator, power of 

attorney, or medical proxy?

NHIS-D (1994-

1995)

If you do not live with a family member, did you choose the place you are 

living?

NHIS-D (1994-

1995)

Do you decide what to wear, how to spend your money, when to eat, 

and when to go to bed?

NHIS-D (1994-

1995)

Lives with a family member as an adult

NHIS-D (1994-

1995)

Had proxy respondent because of a disability

c. Expected Duration 

Both ID and DD are conceptualized as lifelong conditions that are first apparent during the 

developmental period, and for which the impact of the conditions can be reduced through the 

application of supports. The DD Act definition specifies that the condition will continue 

indefinitely and require ongoing services and supports. AAIDD notes that with appropriate 

personalized supports over a sustained period, the life functioning of the person with ID 

generally will improve (Schalock, 2010). While the workgroup recognized that expected duration 

is an important consideration for physical limitations (where limitations following an injury are 

less likely to be enduring), this is less of a concern with ID and DD that are less transitory in 

nature. The workgroup concluded that “expected duration” was a less pressing priority than 

others for developing questions for future identification of people with IDD.
Identifying People with IDD in National Surveys

42

IV. Methodological Considerations 

Appropriate and rigorous surveillance work in IDD requires attention to many methodological

details. The workgroup endorsed the following four methodological considerations to be the 

most relevant for its purposes: small sample size, benchmarking the prevalence of ID and DD 

from 2015 and beyond (to align with the data requirements of the HHS Healthy People initiative), 

developing and cognitively testing items, and producing comparable measures across culture, 

language, race, and ethnicity. Each are briefly discussed below.

 

A. Small sample sizes 

 

The low prevalence of IDD in the U.S. population results in small sample sizes (along with other 

barriers to surveying this population) in virtually all national surveys. A strategy commonly used 

by researchers is to pool data across multiple years (e.g., Dixon-Ibarra & Horner-Johnson, 2014). 

This requires that the same question(s) are repeated across multiple years. The workgroup

recognizes that, even with pooling across years, the small sample sizes constrain the types of 

analyses that are possible. Another strategy to increasing the sample size would require 

oversampling in specific years.

B. Benchmarking 

Several sources can provide benchmark estimates of the number of people with IDD in the 

United States, including public health surveillance, administrative data, and nationally 

representative surveys. The federal partners are currently working together to determine the 

number of years of data that will best benchmark a current national prevalence rate of IDD. The 

current collaborative thinking is that three years of survey data from the NHIS to extrapolate IDD 

data will give an accurate benchmark for overall prevalence that can be used for future regular 

intervals of IDD prevalence. Each data source uses different methods to identify individuals and 

produces different prevalence estimates. Thus, it is important to note which segments of the 
Identifying People with IDD in National Surveys

43

population are included and excluded (i.e., age, type of disability), and whether there is 

adequate sampling for race and ethnicity when considering estimates for benchmarking. 

C. Item development and cognitive testing 

The workgroup collaborated with the National Center for Health Statistics (NCHS) to learn about 

the types of information needed to develop and cognitively test items for possible inclusion in 

the NHIS. The Collaborating Center for Questionnaire Design and Evaluation Research (CCQDER) 

at NCHS develops and cognitively tests a variety of questions for inclusion in data collection 

activities. The CCQDER has conducted multiple rounds of cognitive testing of function questions 

for both children and adults for, among others, the Washington Group and the United Nations 

Children’s Fund. The CCQDER testing has demonstrated the difficulties associated with 

developing questions to identify substantial functional limitations in learning for adults. Similarly, 

translating the concept of self-direction into a viable survey measure for research purposes has 

been difficult.

The workgroup suggests continued collaboration with NCHS’ CCQDER to conduct development 

and cognitive testing of those constructs identified as important but missing in validated survey 

items. This collaborative work conducted with the CCQDER would include addressing the known 

issues associated with the prior work in these constructs as well as potential development of 

new items.

D. Including racial ethnic, and linguistically diverse populations 

Title VI of the Civil Rights Act of 1964 states: “No person in the United States shall, on the 

grounds of race, color, or national origin be excluded from participation in, be denied the 

benefits of, or be otherwise subjected to discrimination under any program or activity receiving 

Federal financial assistance” (Pub. L. No. 88-352). This Act has implications for the importance of 

ensuring the inclusion of racially, ethnically, and linguistically diverse populations in surveys that 

are funded by the federal government. Moreover, beyond any statutory requirements, when any 
Identifying People with IDD in National Surveys

44

group is excluded from the survey, surveillance is incomplete and the unique needs of excluded

groups can neither be identified nor met. Including diverse populations in surveys requires that 

the survey design incorporates a sampling frame that contains these populations and, ideally,

oversamples for underrepresented racial, ethnic and linguistic minority groups. It also requires 

that the construction of the items and instructions for the questionnaire are appropriate for 

diverse populations who reside in the U.S., its territories, and tribal communities. This includes

but is not limited to individuals with disabilities, those who are not literate or have low literacy 

skills, and individuals who are deaf or hard of hearing (Goode, Jones, Christopher & Brown, 2017; 

USHHS, 2014).

The HHS Action Plan to Reduce Racial and Ethnic Health Disparities (2011) provides guidance for 

reducing disparities in health and health care for diverse populations (HHS Action Plan to reduce 

Racial and Ethnic Health Disparities). Purposeful attention to cultural and linguistic differences is 

particularly important for people with IDD, given recent evidence of compounded health 

disparities at the intersection of disability, race, and ethnicity. These studies demonstrate 

important variability in health disparities by race and ethnicity for people with disabilities 

(Horner-Johnson & Dobbertin, 2014; Onyeabor, 2016; Peterson-Besse, Walsh, Horner-Johnson, 

Goode, & Wheeler, 2014). As Goode et al. (2014) noted, health disparities research within both 

racial and ethnic groups and disability groups has typically failed to consider the “multiple 

cultural identities within population groups (p. 6).” As a result, there is a significant need for 

collaborative research to address health disparities where disability, race, and ethnicity intersect

(Yee et al., 2018). The National Standards for Culturally and Linguistically Appropriate Services in 

Health and Health Care (National CLAS standards; HHS, n.d.) outline standards and specify 

practices that are appropriate for culturally sensitive questionnaire design to maximize the 

comparability of survey questions across cultures and reduce measurement error related to 

question design. 

 
Identifying People with IDD in National Surveys

45

E. Data collection in the territories 

 

The understanding of a national level of IDD prevalence is further limited by the omission of the 

U.S. territories in the sampling frames of most national surveillance systems. Although Puerto 

Rico is included in the sampling frame for the Behavioral Risk Factor Surveillance Survey, ACS, 

and SIPP, the omission of the other U.S. territories from most population-based surveys and the 

NHIS limits the ability to estimate prevalence and understand health outcomes of all Americans 

with IDD.

 
Identifying People with IDD in National Surveys

46

V. Summary and Conclusions 

There is a compelling need for timely and accurate information on this important population. 

Changes to national health surveillance systems provide a challenge and an opportunity. The

AIDD National Health Surveillance Workgroup is proposing a path toward a unified framework 

for IDD statistics. This report briefly reviews past IDD prevalence and health surveillance work, 

describes the current national surveillance topography and outlines the likelihood that crucial 

national IDD data will fail to be collected unless action is taken. Finally, suggestions are made for 

areas to be measured in prevalence studies (learning, independent living skills, and age of onset) 

and a shorter set of constructs that could help identify IDD for health surveillance research

(communication, self-direction, and expected duration). Methodological considerations to 

facilitate the swift movement to draft, test, and deploy items in national surveys to meet the 

need for national health surveillance of people with IDD are also reviewed.

 

Directions for future actives are offered:

 

1. AIDD/ACL and its partners intend to work with the research staff at the NCHS’ CCQDER to 

construct and cognitively test survey questions that are valid, reliable, and appropriate to 

identify adults and children with IDD, including those from racially and ethnically diverse 

backgrounds. These questions are intended for future use in the NHIS and other surveys 

to identify people with IDD.

2. Once updated and benchmarked prevalence estimates are complete, the workgroup

recognizes the value of regular prevalence survey iterations to guide future fiscal 

projections, policy development, and program planning. The workgroup recognizes that 

as statutes are changed, domains may need to be updated.

3. Continued collaboration across federal agencies and stakeholder groups will support

broader implementation of health surveillance practices in national data collection 

systems that allow for better identification and prevalence estimates of IDD. 
Identifying People with IDD in National Surveys

47

4. The representativeness of national surveillance systems will improve if they consistently 

include people in the U.S. territories. 

With commitment and collaboration across federal, state, public, and private partners, adults 

with IDD will become visible in health surveillance data so that their services, support, and other 

needs can be understood and addressed across public and private sectors.

 It always seems impossible until it is done.

-Nelson Mandela
Identifying People with IDD in National Surveys

48

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Identifying People with IDD in National Surveys

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Appendices 

Appendix A: Comparing ID (AAIDD) and DD (DD Act) 

Standard Intellectual Disability (AAIDD) Developmental Disabilities (DD Act 

of 2000) 

Age of onset Before age 18 Before age 22

Cause Based on biomedical, social, 

behavioral, and educational risk 

factors

Attributable to mental or physical 

impairments

Severity 2 standard deviations below the 

mean on standardized tests

Severe, resulting in substantial 

functional limitations in three areas

Duration Lifelong Continues indefinitely; 

Of lifelong or extended duration

Supports needed An important purpose of 

describing limitations is to develop 

a profile of needed supports. With 

appropriate personalized supports 

over a sustained period, the life 

function of the person with ID 

generally will improve

Requires a combination and 

sequence of special, 

interdisciplinary, or generic 

services, individualized supports, or 

other forms of assistance that are 

individually planned and 

coordinated

Practice Issues

State agencies may establish 

eligibility criteria for services that 

do not perfectly align with the 

AAIDD definition of ID. For 

example, a state may expand their 

service recipient pool to include 

those with "related conditions" 

such as autism spectrum disorder, 

cerebral palsy, spina bifida, 

epilepsy, and hydrocephalus

whose needs are similar to those 

of a person with ID 

Children ages 9 years or younger 

who have a substantial 

developmental delay or specific 

congenital or acquired condition, 

may be considered to have a 

developmental disability without 

meeting 3 or more of the criteria ... 

if the individual, without services 

and supports, has a high probability 

of meeting those criteria later in 

life.

Domains Substantial Limitations in 

Cognitive and Adaptive behavior 

Substantial Functional Limitations 

Cognitive Intellectual functioning, or 

intelligence, is a general mental 

ability that includes reasoning, 

planning, solving problems, 

thinking abstractly, 

comprehending complex ideas, 

learning quickly, and learning from 

experience

Learning
Identifying People with IDD in National Surveys

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Adaptive behavior

(the collection of 

conceptual, social, 

and practical skills 

that are learned 

and performed by 

people in their 

everyday lives)

Conceptual skills—language and 

literacy; time, and number 

concepts;

Learning

Adaptive behavior

(the collection of 

conceptual, social, 

and practical skills 

that are learned 

and performed by 

people in their 

everyday lives)

Social skills—interpersonal skills, 

social responsibility, self-esteem, 

gullibility, naïveté (i.e., wariness), 

social problem solving, and the 

ability to follow rules/obey laws 

and to avoid being victimized.

Receptive and expressive 

communication

Adaptive behavior

(the collection of 

conceptual, social, 

and practical skills 

that are learned 

and performed by 

people in their 

everyday lives)

Practical skills—activities of daily 

living (personal care), occupational 

skills, healthcare, travel/ 

transportation, schedules/ 

routines, safety, use of money, use 

of the telephone.

Capacity for independent living, 

self-care, economic self-sufficiency, 

mobility, and self-direction

 
Identifying People with IDD in National Surveys

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Appendix B. Items in population-based surveys used to identify ID or DD 

 

The Developmental Disabilities Act of 2000 defines developmental disabilities (DD) based on the

age at onset of disability, severity of disability, expected duration of disability, and the presence 

of substantial functional limitations in at least three of seven domains. The seven domains 

include self-care (also known as activities of daily living[ ADL]), independent living (also known as 

instrumental activities of daily living [IADL]), communication, economic self-sufficiency, mobility, 

learning, and self-direction. 

The following tables list items from population-based surveys that assess the elements of the 

Developmental Disabilities Act definition of DD and the American Association on Intellectual and 

Developmental Disabilities (AAIDD) definition of intellectual disability (ID):

• Table B1 2016 National Health Interview Survey (NHIS) - adults

• Table B2 1994-1995 National Health Interview Survey - Disability Survey (NHIS-D) adults 

• Table B3 2008-2013 Survey of Income and Program Participation (SIPP) adults 

• Table B4 2008-2013 SIPP children

• Table B5 World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) 

The 2016 NHIS survey included items covering five of the seven functional limitations described 

in the DD Act definition of DD. It did not include items on limitations in self-direction or learning, 

nor did it ask age at onset of disability or if the limitation was expected to continue indefinitely. It 

did ask whether ID, Down syndrome, cerebral palsy, epilepsy, spina bifida, or hydrocephalus was 

the primary cause of reported limitation. 
Identifying People with IDD in National Surveys

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National Health Interview Survey (2016) 

Table B1. 2016 NHIS Items used to screen adults for intellectual or developmental disabilities. 

Survey Subscale Item Stem Limitation Type 

NHIS AFD Difficulty with self-care self-care

NHIS Family Need help with personal care self-care

NHIS Family Need help with bathing/showering self-care

NHIS Family Need help dressing self-care

NHIS Family Need help eating self-care

NHIS Family Need help in/out of bed or chairs self-care

NHIS Family Need help using toilet self-care

NHIS Family Need help with routine needs self-care

NHIS AFD Difficulty communicating in usual language communication

NHIS Interviewer Did the person require a proxy respondent because 

of disability related limitations

communication

NHIS Family Condition now keeps from work economic

NHIS Family Limited in kind/amount of work economic

NHIS Sample 

Adult

Difficulty w/ social activities social 

participation

NHIS Sample 

Adult

Difficulty w/ leisure activities social 

participation

NHIS Sample 

Adult

Difficulty w/ shopping Independent 

living

NHIS AFD Difficulty walking or climbing steps Mobility

NHIS AFD Someone's assistance with getting around Mobility

NHIS Sample 

Adult

Difficulty walking quarter mile Mobility

NHIS Sample 

Adult

Difficulty 10 steps Mobility

NHIS Sample 

Adult

Difficulty standing two hours Mobility

NHIS Family Need help to get around house Mobility

NHIS Family Have difficulty walking without equipment Mobility

 
Identifying People with IDD in National Surveys

60

National Health Interview Survey-Disability Survey (1994/95) 

 

Table B2. 1994-95 NHIS-D items used to identify adults with IDD. 

Survey Subscale Item Stem Key Element 

NHIS-D Person currently has mental 

retardation

Diagnosis of ID

NHIS-D Mental retardation was indicated as 

the cause of age-specific general 

activity limitations. General activity 

limitations included limitations in play 

for children ages 5 and younger, 

limitations in school activities for 

children ages 5 to 17, limitations in 

work for adults ages 18 to 69, and 

overall limitations in activities for 

people of all ages.

Diagnosis of ID

NHIS-D Mental retardation was identified as 

the primary cause of limitations in 

communication, getting along with 

others, activities of daily living, 

instrumental activities of daily living, 

and other functional limitations; or if 

mental retardation was the ICD code 

listed as the reason the person had a 

doctor’s visit, a physician consultation 

regarding communication, or as the 

reason for receiving occupational 

therapy.

Diagnosis of ID

NHIS-D Has autism, cerebral palsy, Down 

syndrome, spina bifida, or 

hydrocephalus. Or, Does condition file 

list a related condition as the cause of 

either age-specific general activity 

limitations in the Core Survey, as the 

cause of specific activity limitations 

(e.g., communicating, getting along 

with others) or as the reason for 

receiving various services (e.g., 

occupational or physical therapy) in 

the Phase 1 Disability Supplement AND 

a learning disability AND significant 

functional learning limitations.

Diagnosis of conditions 

associated with ID
Identifying People with IDD in National Surveys

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NHIS-D Has DD based on DD Act definition of 

three or more significant functional 

limitations occurring before age 22 

expected to continue indefinitely.

Has DD

NHIS-D A person 18 years or older “has serious 

difficulty” or “cannot use” the 

telephone.

Communication/Expressive 

or Receptive Language

NHIS-D A person 5 years or older “has serious 

difficulty communicating so the family 

can understand” or “has serious 

difficulty understanding others when 

they talk or ask questions.”

Communication/Expressive 

or Receptive Language

NHIS-D Difficulty communicating with people 

outside of the family.

Communication/Expressive 

or Receptive Language

NHIS-D Difficulty communicating in usual 

language.

Communication/Expressive 

or Receptive Language

NHIS-D Has dx of mental retardation or had 

serious difficulty learning how to do 

things that most people their age are 

able to learn AND does not have 

Alzheimer’s or another senility 

disorder AND less than 2 years postsecondary education completed.

Learning

NHIS-D Has a learning disability. Learning

NHIS-D A person 5 years or older “has a lot of 

difficulty” or “is unable” to dress, eat, 

bathe, get in and out of bed or chairs, 

use the toilet, or get around the 

house.

Self-care

NHIS-D A person 18 years or older “requires 

help or supervision” or “has a lot of 

difficulty with” or “is unable” to 

prepare meals, shop for personal items 

or medicine, manage his or her money, 

do light work around the house (such 

as doing dishes, straightening up, light 

cleaning or taking out the trash) or do 

heavy work around the house.

Independent Living

NHIS-D Activities in last two weeks: meet with 

friends or neighbors, talk on phone 

with friends or neighbors, meet with 

relatives or family, talk on phone with 

relatives or family, attend religious 

Social participation
Identifying People with IDD in National Surveys

62

services, attend events, eat at a 

restaurant.

NHIS-D Go out every day, did not leave home 

at all in last two weeks, satisfied with 

frequency of social activities.

Social participation

NHIS-D A person 18 years or older “has 

participated in” or is “on the waiting 

list” for a sheltered workshop, 

transitional work training, supported 

employment or a day activity center; 

or “is unable to work” because of a 

mental or emotional problem.

Economic Self-Sufficiency

NHIS-D A person 18 years or older “has never 

been able to work” or “is currently 

unable to work because of a mental or 

emotional problem” or “is limited in 

kind or amount of work” due to a 

limitation; or “has trouble finding or 

keeping a job or doing job tasks 

because of a mental or emotional 

problem.”

Economic Self-Sufficiency

NHIS-D A person 18 years or older has or 

needs a “case manager to coordinate 

personal care, social or medical 

services” or “has a court appointed 

guardian” during the last 12 months.

Self-direction

NHIS-D A person 5 years or older, because of a 

physical, mental or emotional 

problem, “needs to be reminded or 

have someone close by” for dressing, 

eating, bathing, toileting, or 

transferring.

Self-direction

NHIS-D A person 5 years or older “has 

difficulty” or “is unable” to walk up 10 

steps, walk three city blocks, or getting 

in or out of bed or chairs.

Mobility

NHIS-D Difficulty walking or climbing steps Mobility

NHIS-D Equipment/help to get around Mobility
Identifying People with IDD in National Surveys

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NHIS-D Uses special equipment Mobility

NHIS-D Have difficulty walking without 

equipment

Mobility

NHIS-D Use cane Mobility

NHIS-D Use walker Mobility

NHIS-D Use crutches Mobility

NHIS-D Use wheelchair scooter Mobility

NHIS-D Artificial limb Mobility

NHIS-D Someone's assistance with getting 

around house

Mobility

NHIS-D Other equipment Mobility

NHIS-D Difficulty walking 100 yards without 

aids

Mobility

NHIS-D Difficulty walking 1/3 mile without aids Mobility

NHIS-D difficulty walking quarter mile Mobility

NHIS-D Difficulty up/down 12 steps Mobility

NHIS-D Difficulty up/down 10 steps Mobility

 

 
Identifying People with IDD in National Surveys

64

Survey of Income and Program Participation (2008-2013) 

 

Table B3. 2008-2013 SIPP items used to identify adults with IDD 

Survey Subscale Item Stem Key Element 

SIPP IDD

Screens: 

Adult

I have recorded that [fill TEMPNAME] health is fair 

or poor. Which condition or conditions cause these 

difficulties? (Age 15+ years only) (Item ADQ33)

[SHOW CONDTION FLASHCARD – 30 conditions 

including cerebral palsy, epilepsy, learning 

disability, mental retardation]

Conditions associated 

with DD

SIPP IDD

Screens: 

Adult

Any Others? [UP TO THREE} Conditions associated 

with DD

SIPP IDD

Screens: 

Adult

Which of the conditions that you mentioned do you 

consider to be the main reason for [fill 

PTEMPNAME] difficulties? 

[FILL IN UP TO THREE CONDITIONS (Age 15+ years 

only- Item ADQ35)] 

Conditions associated 

with DD

SIPP IDD

Screens: 

Adult

Does [fill TEMPNAME] have – [(Age 15+ years only) 

(Item ADQ39)]

(1) Yes (2) No

a. A learning disability such as dyslexia?

Conditions associated 

with DD

SIPP IDD

Screens: 

Adult

b. Mental retardation? Conditions associated 

with DD: ID diagnosis

SIPP IDD

Screens: 

Adult

c. A developmental disability such as autism or 

cerebral palsy?

Conditions associated 

with DD

SIPP IDD

Screens: 

Adult

d. Alzheimer's disease or any other serious problem 

with confusion or forgetfulness?

Conditions that inform 

DD determination (rule 

out)

SIPP IDD

Screens: 

Adult

e. Any other mental or emotional condition? Conditions associated 

with DD

SIPP IDD

Screens: 

Adult

I have recorded that [fill TEMPNAME] [fill HAVHAS] 

a limitation in working [fill 

TEMPQ47]. Which condition or conditions cause this 

limitation? 

Economic selfsufficiency
Identifying People with IDD in National Surveys

65

Survey Subscale Item Stem Key Element 

[SHOW CONDTION FLASHCARD– 30 conditions 

including cerebral palsy, epilepsy, learning 

disability, mental retardation]

[(Age 16-72 years only) (Item ADQ47)]

SIPP IDD

Screens: 

Adult

Any Others? [UP TO THREE] 

Specify the exact "Other" condition that causes your 

work limitation. 

[(Item ADQ47A) (Age 16-72 years only)]

Economic selfsufficiency

SIPP IDD

Screens: 

Adult

Which of the conditions that you mentioned do you 

consider to be the main reason for [fill 

PTEMPNAME] limitation?

[FILL IN UP TO THREE CONDITIONS– 30 conditions 

including cerebral palsy, learning disability, mental 

retardation]

[(Age 16-72 years only) (Item ADQ48)]

Economic selfsufficiency

SIPP IDD

Screens: 

Adult

For how long [fill HAVHAS] [fill TEMPNAME] needed 

help of another person? 

(1) Less than 6 months (2) 6 to 11 months (3) 1 to 2 

years (4) 3 to 5 years (5) More than 5 years

[(Age 15+ years only) (Item ADQ29)]

Age of Onset

SIPP IDD

Screens: 

Adult

When did [CONDITION]first begin to bother [fill 

TEMPNAME]?

[ENTER 4 DIGIT YEAR (Item ADQ36)]

Age of Onset

SIPP IDD

Screens: 

Adult

Is this condition expected to last for at least 12 

more months?

(1) Yes (2) No

[(Items ADQ38, ADQ39, ADQ47, )]

Duration
Identifying People with IDD in National Surveys

66

Table B4. 2008-2013 SIPP items used to identify children with IDD 

Survey Subscale Item Stem Element 

SIPP Child IDD 

Screen

Does ... have a serious physical or mental 

condition or a developmental delay that limits 

ordinary activities? 

(1) Yes (2) No

[(Age less than 6 years only) (Item CDQ1A)]

Limitation

SIPP Child IDD 

Screen

Does ... have a learning disability 

(1) Yes (2) No

[(Age >= 6 and < 15 years only) (Item CDQ6.1)]

Condition association 

with DD

SIPP Child IDD 

Screen

Does ... have mental retardation?

(1) Yes (2) No

[(Age >= 6 and < 15 years only) (Item CDQ6.2)]

ID diagnosis

SIPP Child IDD 

Screen

Does ... have a developmental disability such as 

autism or cerebral palsy?

(1) Yes (2) No

[(Age >= 6 and < 15 years only) (Item CDQ6.3)]

Condition association 

with DD

SIPP Child IDD 

Screen

Does ... have any other developmental 

condition for which he or she has received 

therapy or diagnostic services?

(1) Yes (2) No

[(Age >= 6 and < 15 years only) (Item CDQ6.5)]

Diagnosis or treatment 

for condition 

association with DD

SIPP Child IDD 

Screen

I have recorded that ... has difficulty with 

certain activities. Which condition or conditions 

cause this difficulty? 

[SHOW CHILDHOOD CONDITIONS FLASHCARD 

– 23 conditions including cerebral palsy, 

epilepsy, learning disability, mental 

retardation]

[Age >= 6 and < 15 years only) (Item CDQ29.1)]

Condition association 

with DD

SIPP Child IDD 

Screen

Any Others? [UP TO THREE] Condition association 

with DD
Identifying People with IDD in National Surveys

67

World Health Organization Disability Assessment Schedule (WHODAS 2.0) 

Table B5. WHODAS 2.0 items describing DD Act functional limitations in adults with DD

DD Act Domain Question: In the last 30 days how much difficulty did you have in:

Learning • Analyzing and finding solutions to problems in everyday life

• Learning a new task, for example, learning how to get to a new place

Communication • Generally understanding what people say

• Starting and maintaining a conversation

Independent Living • Staying by yourself for a few days

• Doing the most important household tasks well

• Getting your household work done as quickly as needed

Other Domains Question: How much of a problem do you have:

Social participation • Dealing with people you do not know

• Maintaining a friendship

• Getting along with people who are close to you

• Making new friends

• Joining in community activities

Recreation • Doing things for relaxation or pleasure by yourself

Table adapted from Ustuen et al, (2010)