Number 69 n November 1, 2013

Self-report of Diabetes and Claims-based Identification

of Diabetes Among Medicare Beneficiaries

by Hannah R. Day, Ph.D., and Jennifer D. Parker, Ph.D., Office of Analysis and Epidemiology

Abstract

Objective—This report compares self-reported diabetes in the National

Health Interview Survey (NHIS) with diabetes identified using the Medicare

Chronic Condition (CC) Summary file.

Background—NHIS records have been linked with Medicare data from the

Centers for Medicare & Medicaid Services. The CC Summary file, one of

several linked files derived from Medicare claims data, contains indicators for

chronic conditions based on an established algorithm.

Methods—This analysis was limited to 2005 NHIS participants aged 65 and

over whose records were linked to 2005 Medicare data. Linked NHIS

participants had at least 1 month of fee-for-service Medicare coverage in 2005.

Concordance between self-reported diabetes and the CC Summary indicator for

diabetes is compared and described by demographics, socioeconomic status,

health status indicators, and geographic characteristics.

Results—Of the Medicare beneficiaries in the 2005 NHIS, 20.0% selfreported diabetes and 27.8% had an indicator for diabetes in the CC Summary

file. Of those who self-reported diabetes in NHIS, the percentage with a CC

Summary indicator for diabetes was high (93.1%). Of those with a CC Summary

indicator for diabetes, the percentage self-reporting diabetes was comparatively

lower (67.0%). Statistically significant differences by subgroup existed in the

percentage concordance between the two sources. Of those with self-reported

diabetes, the percentage with a CC Summary indicator differed by sex and age.

Of those with a CC Summary indicator for diabetes, the percentage with

self-reported diabetes differed by age, self-rated health, number of self-reported

conditions, and geographic location.

Conclusions—Among Medicare beneficiaries who self-reported diabetes in

NHIS, a high concordance was observed with identification of diabetes in the CC

Summary file. However, among Medicare beneficiaries with an indicator for

diabetes in the CC Summary file, concordance with self-reported diabetes in

NHIS is comparatively lower. Differences exist by subgroup.

Keywords: record linkage • National Health Interview Survey • Chronic

Condition Summary file

Introduction

Diabetes is an endocrine disorder

characterized by impaired insulin

production or insulin resistance, which

leads to increased blood glucose levels

(1). In adults aged 65 and over, diabetes

can be classified as Type 1 (previously

called juvenile diabetes), or Type 2

(previously called adult-onset diabetes)

(1). Type 1 diabetes is an autoimmune

disorder with a strong genetic

component, and Type 2 diabetes is an

acquired disease with evidence of

genetic components. Type 2 diabetes is

responsible for 90%–95% of diabetes

cases in the United States (1). Risk

factors for Type 2 diabetes include age,

obesity, ethnicity, and insufficient

physical activity (1). Complications of

the disease include heart disease,

myocardial infarction, stroke, lower

extremity infection, amputation, and

blindness (1–3). In older adults, diabetes

is associated with higher morbidity and

all-cause mortality (2). Diabetes is one

of the 10 most expensive disease

categories among Medicare beneficiaries

(4). Higher costs result from greater

service utilization, especially more

hospital stays and longer lengths of stay,

more physician visits, and greater

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Center for Health Statistics 
Page 2 National Health Statistics Reports n Number 69 n November 1, 2013

medication use compared with adults

not having diabetes (5).

Most studies of diabetes in the

Medicare population use administrative

Medicare records collected for billing

purposes. The use of Medicare claims to

identify people with diabetes has been

examined using the Medicare Current

Beneficiary Survey (MCBS), a

nationally representative sample of the

Medicare population with survey records

linked to Medicare claims. One recent

MCBS study using survey data from

2004 estimated that 20.3% of

noninstitutionalized Medicare

beneficiaries reported being told by a

doctor that they had diabetes (6). A

previous comparison of MCBS selfreport data for 1992–1993 with

Medicare claims data from 1992–1993

found the percentage of patients

identified in claims data varied widely

depending on the algorithm and

reference period used (7). Using an

algorithm looking for ‘‘one or more

diagnoses of diabetes in any Medicare

claim file’’ over a 2-year period, 79% of

those who self-reported diabetes were

identified in the Medicare data, but only

71% of those with a claim for diabetes

in the Medicare data had self-reported

diabetes (7). These studies highlight that

concordance between self-report and

claims data is not always 100%. People

who self-report diabetes may not always

be identified by Medicare claims, and

not all people who have Medicare

claims for diabetes will self-report the

disease (7). A previous National Center

for Health Statistics (NCHS) study using

data from the Health Interview

Evaluation Survey, conducted in 1990,

compared self-report with medical

records and found more instances where

diabetes was present in the medical

record but not reported in the interview,

than instances where diabetes was

reported in the interview but not present

in the medical record (8).

Differences between survey and

administrative data can lead to varying

prevalence estimates, with estimates

based on self-report often being lower

than claims-based estimates. Examples

of diabetes prevalence estimates for

noninstitutionalized adults aged 65 and

over based on self-report include the

20.3% prevalence estimate in the

noninstitutionalized 2004 MCBS

population, an estimate of 20.5% in

adults aged 65 and over from the 2011

National Health Interview Survey

(NHIS), and an estimate of 17.0% in the

interview component of the 2005–2006

National Health and Nutrition

Examination Survey (NHANES)

(6,7,9,10). In addition to identifying

diabetes using self-report or claims, the

NHANES study also conducts

examinations with fasting plasma

glucose and oral glucose tolerance tests.

In NHANES, as much as 46.2% of

diabetes was neither diagnosed nor

self-reported (9). The prevalence for

adults aged 65 and over based on

examination data in 2005–2006

NHANES was nearly twice that based

on interview, at 31.6% (9).

In contrast, based on Medicare

claims data, Margolis et al. estimated a

diabetes prevalence of 26.5%–28.0% in

Medicare fee-for-service (FFS)

beneficiaries aged 65 and over in

2006–2008 (11), and another study

estimated a prevalence of 24.3% in adult

Medicare beneficiaries of all ages using

the 2005 Medicare Chronic Conditions

(CC) Summary file (12).

The differences between self-report,

administrative, and examination data

have important implications for

researchers who wish to use either

survey or administrative data to examine

chronic diseases in subpopulations, or

who wish to adjust for diabetes in these

subpopulations. Knowing which

subpopulations differ significantly with

respect to what percentage of

participants who self-report have

administrative indicators of diabetes, or

the percentage of participants with

administrative indicators who self-report

diabetes, will help researchers know the

limitations of using either source of data

in their studies and help them choose

the best data source, or combination of

data sources, for their study population.

There are strengths and weaknesses

in using either self-report or

administrative databases for studies of

diabetes. Self-report data include

detailed information gathered directly

from participants and are subject to

possible response bias. However,

population health surveys provide

additional information on characteristics

not included in administrative data,

including income, education, and marital

status. In contrast, administrative

databases often include detailed cost and

service use information and allow for

longitudinal tracking of patients, but

administrative data are created for

billing purposes and often lack

demographic, health, and risk factor

information (13). Further, although

Medicare covers the majority of adults

aged 65 and over, the Centers for

Medicare & Medicaid Services (CMS)

receives only the detail needed to

identify diabetes from claims for FFS

beneficiaries. Medicare beneficiaries

have the option to enroll in traditional

FFS or in Medicare Advantage

(MA)—also referred to as managed care

organizations or Medicare Part C. In

2005, 85% of Medicare beneficiaries

were in the FFS program (14). Some

studies have found FFS beneficiaries to

be older and in poorer health (15–17);

however, other studies have shown that

the difference between MA and FFS

may be decreasing (18,19). The

accuracy of survey response in FFS

compared with MA enrollment is

unknown.

The CC Summary file was created

from CMS claims to allow researchers

to easily identify Medicare beneficiaries

with claims for 21 selected chronic

conditions (including diabetes, selected

cancers, heart disease, hip fracture, and

others), based on published algorithms.

To identify individual diseases or

conditions from claims data without the

CC Summary file, multiple Medicare

files must be combined, using various

algorithms to identify claims specific to

each disease (7). The CC Summary file

has been used to study prevalence of

comorbidity (20), multiple chronic

conditions (12), functional capacity of

home health care patients (21), arthritis

screening and prevention (22), and other

topics important to the Medicare

population (23).

The goal of this report is to

compare self-reported diabetes in the

2005 NHIS—currently the most recent

year of NHIS linked to Medicare

data—with an indicator for diabetes in

the 2005 CC Summary file. The

NHIS–Medicare linked data provide a
National Health Statistics Reports n Number 69 n November 1, 2013 Page 3

unique opportunity to examine and

compare the prevalence of diabetes

derived from each data source. The

large size of NHIS and its detailed

questionnaire allow identification of

demographic, geographic, and healthrelated factors associated with

discrepancies between the data sources.

Data Sources

NHIS

NHIS uses a cross-sectional,

multistage area probability design to

collect data on demographic and

health-related information from the

civilian noninstitutionalized U.S.

population. NHIS has been conducted

continuously since 1957 by the Centers

for Disease Control and Prevention’s

NCHS, although both the survey design

and instrument have changed over time.

Currently, the design oversamples black,

Hispanic, and Asian persons. The NHIS

sample is currently drawn from each

state and the District of Columbia. The

survey consists of household, family,

Sample Adult, Sample Child, and

supplemental components. Limited

demographic information is collected on

all individuals living in a house for the

household file. The family component of

the questionnaire collects demographic

information on each member in a family

from a knowledgeable adult (family

respondent), along with information on

health status, limitations, health care

access utilization, and insurance. From

each family, one sample adult is

randomly selected to answer more

in-depth questions about their own

health. Information on one sample child

per family is collected if children are

present in the family.

Self-reported diabetes in the 2005

NHIS was measured by asking sample

adults, ‘‘Other than during pregnancy,

have you EVER been told by a doctor

or health professional that you have

diabetes or sugar diabetes?’’ Participants

could respond ‘‘yes,’’ ‘‘no,’’ ‘‘borderline

diabetes,’’ ‘‘refused,’’ or ‘‘don’t know.’’

For this report, participants were

considered to have diabetes if they

responded ‘‘yes’’; participants who

responded ‘‘no’’ were considered not to

have diabetes by self-report.

Descriptive characteristics examined

in this report include demographic

characteristics (age, race and ethnicity,

marital status, and sex), socioeconomic

status (education and poverty level),

geographic characteristics (metropolitan

residence status and region of country),

and health risk factor variables (selfrated health, number of reported chronic

health conditions, and obesity). Age at

the time of interview was categorized

into two groups: 65–74, and 75 and

over.

Race and ethnicity are collected

separately in NHIS, first by asking if the

participant is Hispanic or Latino, then

by asking the participant’s race or races.

For this report, race and ethnicity were

combined into four categories: nonHispanic white, non-Hispanic black,

Hispanic, and all other races and

ethnicities. Estimates for beneficiaries

reporting all other races and ethnicities

are not presented due to the small

number of people in this group;

however, these beneficiaries are

included in statistics based on other

variables.

Socioeconomic status was

represented by examining education and

poverty level. Two education categories

were created: high school education or

lower (no high school diploma, high

school diploma, or General Educational

Development high school equivalency

certificate), and some college or more.

Because income data are often missing,

multiply imputed income files were used

to categorize annual family income into

groups of below 100% of the federal

poverty level (poor), 100%–199% of

poverty level (near poor), or 200% of

poverty level or more (non-poor). Five

sets of multiply imputed income were

combined and analyzed using

established methods (24).

Geographic variables of

metropolitan residence status [within a

metropolitan statistical area (MSA) and

outside an MSA] and region of country

(Northeast, Midwest, South, and West)

were used. Definitions of MSA

compared with outside an MSA used the

2006 NCHS urban–rural classification

scheme based on the 2000 census and

Office of Management and Budget

standards for defining metropolitan and

micropolitan statistical areas (25). The

NCHS Urban–Rural Classification

Scheme for Counties includes six

categories: large central metropolitan,

large fringe metropolitan, medium

metropolitan, small metropolitan,

micropolitan, and noncore. Due to small

cell sizes, subgroups smaller than the

metropolitan categories (large central

metropolitan, large fringe metropolitan,

medium metropolitan, and small

metropolitan) were not examined

compared with nonmetropolitan

categories (micropolitan and noncore)

(25).

Health risk factor variables from

NHIS included participant self-perceived

health status (fair or poor compared

with excellent, very good, or good),

obesity [body mass index (BMI) greater

than 30 compared with 29 or less], and

number of reported health conditions.

The total number of health conditions

variable was created from a set of

self-report NHIS variables and was

dichotomized into 0–1 or 2 or more

conditions. Conditions included in the

total number of health conditions

variable included hypertension, coronary

heart disease, angina, myocardial

infarction, stroke, emphysema, asthma,

kidney disease, liver disease, and

cancers other than nonmelanoma skin

cancer. All NHIS self-reported chronic

conditions that were similar to those in

the CC Summary file were included in

this count. Because the self-reported

conditions and the CC Summary file

differed slightly with regard to the

conditions available, this count was

intended to be an indicator of selfreported number of conditions only.

Linked NCHS–CMS data

The NCHS record linkage program

has linked various NCHS surveys to

administrative records from CMS and

the Social Security Administration

(SSA) under an interagency agreement

among NCHS, CMS, SSA, and the

Office of the Assistant Secretary for

Planning and Evaluation (26). The 2005

NHIS has been linked to 1999–2007

Medicare claims (26). NHIS participants
Self-report Chronic Conditions 

Summary file 

Percent 20 

40 

30 

10 

0 

Ι 95% confidence inter val.
 

NOTES: Categories are not mutually exclusive. For detailed data, see Table 1 in this report. 


SOURCES: CDC/NCHS, 2005 National Health Inter view Sur vey (NHIS) linked to 2005 Medicare data.
 

Page 4 National Health Statistics Reports n Number 69 n November 1, 2013

who had sufficient personal identifier

information (PII), who did not refuse to

provide their Social Security number

(SSN) or Health Insurance Claim

number, and who had an SSN verified

by the SSA Enumeration Verification

System were eligible for linkage to

CMS and SSA records (26). Among the

linkage-eligible, if a participant’s PII

matched the CMS denominator file on

SSN, date of birth (month, day, year),

and sex, the participant was considered

to be a match to CMS records (26). In

2005, the family respondent and sample

adult were asked to provide their SSN.

Initial data were available for 31,428

sample adults in NHIS 2005. Of these,

6,078 were aged 65 and over at the time

of survey and, of these, 2,554 sample

adults aged 65 and over were linkageeligible. Of these, 98% of the sample

adults (n = 2,499) were linked with the

2005 Medicare CC Summary file.

Available Medicare files for

1999–2007 include the denominator file

(with information on demographics and

plan coverage), the carrier file

(noninstitutional claims and provider

claims), the outpatient file (institutional

outpatient claims), home health agency

claims (claims for home health

services), the hospice file, and a durable

medical equipment file. Utilization

claims data can be obtained from the

Medpar file, which contains information

on inpatient hospitalizations and skilled

nursing facilities. The CC Summary file

is available for 2005 and later, and

Part D files are available for 2006 and

later. In addition, NCHS creates a

Summary Medicare Expenditure and

Claims file using information from the

denominator and claims files for use

with the NCHS–Medicare linked data

files.

This analysis uses the 2005 NHIS

data linked to the 2005 Medicare CC

Summary file and the 2005 denominator

file. The 2005 Medicare denominator

file includes enrollment information and

program participation. Only beneficiaries

enrolled in traditional FFS are included

in this analysis, because Medicare does

not receive claims for beneficiaries

enrolled in MA programs. The CC

Summary file summarizes the presence

of 21 conditions by applying algorithms

to the various Medicare claims data. The

2005 CC summary file includes flags

representing claims and eligibility and a

variable indicating the date on which the

clinical component of a condition was

first recorded during 1999–2005. The

algorithm used to define diabetes in the

CC Summary file identified

beneficiaries as having diabetes if they

had, within a 2-year reference period, at

least one inpatient skilled-nursing

facility or home health agency claim, or

two hospital outpatient or carrier claims

(claims data submitted by

noninstitutional providers, including

physicians and supplementary

providers), with codes for diabetes (27).

Methods

Analysis

Study population

The analytic sample includes

linkage-eligible 2005 NHIS sample

adults who were aged 65 and over at the

time of interview, were linked to the

CMS denominator file for 2005, and had

at least 1 month of FFS claims in 2005.

Of the 2,499 sample adults aged 65

and over whose records linked with the

2005 Medicare CC Summary file,

13.3% (n = 331) were excluded due to

not having at least 1 month of FFS

coverage in 2005. The single survey

participant who responded ‘‘don’t

know’’ to the NHIS question about

diabetes, and the 58 participants who

responded ‘‘borderline’’ to the question

about diabetes, were not included in the

primary analysis. Participants who

responded ‘‘borderline’’ were retained

for sensitivity analysis, described in the

‘‘Results’’ section.

In the 2005 NHIS, 20.0% of

Medicare beneficiaries aged 65 and over

reported they had ever had diabetes

(Figure 1, Table 1).

A total of 27.9% of Medicare

beneficiaries aged 65 and over in the

2005 NHIS had a 2005 Medicare CC

Summary indicator for diabetes,

indicating one or more claims for

diabetes from 1999 through 2005

(Figure 1, Table 1).

Statistical analysis

To account for the complex survey

design, SAS-callable SUDAAN version

Figure 1. Diabetes by self-report or Chronic Conditions Summary indicator, among

Medicare beneficiaries aged 65 and over at NHIS interview
National Health Statistics Reports n Number 69 n November 1, 2013	 Page 5 Percent Ι 95% conf idence inter val. 

NOTES: Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 2 in this repor t. 

SOURCES: CDC/NCHS, 2005 National Health Inter view Sur vey (NHIS) linked to 2005 Medicare data. 

0 

20 

40 

60 

80 

100 

Men Women Hispanic NonHispanic 

black 

NonHispanic 

white 

Aged 

65–74 

Aged 75 

and over 

Married Not 

married 

Figure 2. NHIS Medicare beneficiaries with diabetes in Chronic Conditions Summary file among those who self-reported diabetes, by

demographic characteristics

9.3 statistical software was used (RTI

International, Research Triangle Park,

N.C.). All analyses include sample adult

weights for NHIS 2005. To account for

possible differences between adults who

were eligible for the linkage and those

who were not, sample weights were

further adjusted for nonlinkage eligibility

by using the SUDAAN procedure PROC

WTADJUST. With PROC WTADJUST, a

model-based calibration approach was

used to adjust the NHIS sample adult

weights for race and sex (28).

Estimates presented have a relative

standard error (RSE) less than or equal to

30%. The RSE is equal to the standard

error of the estimate divided by the

estimate itself. The RSE is often

multiplied by 100 and expressed as a

percentage. RSEs greater than 30% are

considered unreliable and are not

presented in the report.

Differences in prevalence by CC

Summary file compared with self-report

were not tested for statistical significance

because the two sources were not

measured on independent populations.

Therefore, statements comparing overall

diabetes estimates from Medicare records

with those from self-report should be

considered as observations, and not as

conclusions of a statistical test. For

comparisons among subgroups within

either the CC Summary file or NHIS,

statements such as ‘‘more likely’’ and

‘‘less likely’’ indicate statistical

significance and are chi-squared tests, or

are pairwise tests with Bonferroni

corrections when chi-squared tests

indicated statistical significance (p =

0.05) and more than two categories were

present in a variable.

Results

Characteristics of those

self-reporting diabetes in

2005 NHIS

+	 A total of 93.1% of NHIS diabetes

self-reports had a 2005 CC Summary

indicator for diabetes.

+	 Men were less likely than women to

have a CC Summary indicator

(Figure 2, Table 2).

+	 Medicare beneficiaries aged 65–74

were less likely to have a CC

Summary indicator than beneficiaries

aged 75 and over (Figure 2, Table 2).

+	 No significant differences were seen

in the percentage of beneficiaries who

self-reported diabetes with a CC

Summary indicator by race or

ethnicity, marital status, education,

poverty level, geography, or health

indicators (Figures 2–5, Tables 2–5).

Characteristics of those with

CC Summary indicator

+	 A total of 67.0% having a CC

Summary indicator self-reported

diabetes in the 2005 NHIS.

+	 Beneficiaries aged 65–74 were more

likely to self-report diabetes than

beneficiaries aged 75 and over

(Figure 6, Table 6).

+	 No significant differences were

observed in the percentage who

self-reported diabetes by sex, race

and ethnicity or marital status,

education or poverty status, BMI, or

geography (Figures 6–9, Tables 6–9).

+	 Beneficiaries in the Northeast were

less likely to self-report diabetes than

beneficiaries in any other region

(Figure 8, Table 8).

+	 Beneficiaries who self-reported fair or

poor health were more likely to

self-report diabetes than beneficiaries

in good or excellent health (Figure 9,

Table 9).

+	 Beneficiaries who self-reported two

or more conditions were more likely
100 

80 

60 

40 

20 

0 

High school Some college Below 100% 100%–199% 200% of 

diploma, GED, or more of poverty of poverty poverty 

or less than level level level or more 

high school 

diploma 

Percent Ι 95% confidence inter val.
 

NOTES: Figures are based on Medicare benef iciaries aged 65 and over; for detailed data, see Table 3 in this repor t. 


GED is General Educational Development high school equivalency diploma. Percentage of federal poverty level is
 

based on family income and family size and composition using U.S. Census Bureau pover ty thresholds; missing
 

family income data were imputed.
 

SOURCES: CDC/NCHS, 2005 National Health Inter view Sur vey (NHIS) linked to 2005 Medicare data.
 

100 

80 

60 

Percent 

MSA Not MSA Northeast Midwest South West 

40 

20 

0 

Ι 95% confidence inter val. 

NOTES: Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 4 in this repor t. 


MSA is metropolitan statistical area; MSA status was determined using 2000 census data and 2000 standards for
 

def ining MSAs.
 

SOURCES: CDC/NCHS, 2005 National Health Inter view Sur vey (NHIS) linked to 2005 Medicare data.
 

Page 6 National Health Statistics Reports n Number 69 n November 1, 2013

to self-report diabetes than

beneficiaries with fewer conditions

(Figure 9, Table 9).

Sensitivity analyses

A sensitivity analysis examining

only beneficiaries with 12 months of

FFS in 2005 reduced the sample size

from 2,109 to 1,955; however, results

remained similar. Of the beneficiaries

who self-reported diabetes and had 12

months of FFS, 93.9% of the 1,955

beneficiaries had a CC Summary

indicator, compared with 93.1% of the

2,109 in the full sample who reported

any FFS in 2005. Of the beneficiaries

with a CC Summary indicator and 12

months of FFS, 67.4% of 1,957 persons

self-reported diabetes compared with

67.0% of 2,109 persons with any FFS in

2005.

A separate sensitivity analysis

combined those who answered ‘‘yes’’ to

the diabetes question with those who

responded they had ‘‘borderline’’

diabetes. Of the 478 sample adults who

responded ‘‘yes’’ or ‘‘borderline’’ to the

diabetes question, 429 (90.0%) had

diabetes indicated in the CC Summary

file. Of the sample adults who had a CC

Summary indicator for diabetes, 68.8%

responded ‘‘yes’’ or ‘‘borderline’’ in

NHIS. Of the 58 sample adults aged 65

and over who responded they had

borderline diabetes, 39 had diabetes

indicated in Medicare (65.2%) and 19

did not (34.8%).

Figure 3. NHIS Medicare beneficiaries with diabetes in Chronic Conditions Summary file

among those who self-reported diabetes, by education and poverty level

A final sensitivity analysis revealed

that only 2.7% of the 2,109 beneficiaries

in the full sample had a first recorded

date in the database of 2005, the survey

year. Of those who had a first recorded

date of 2005, 39% self-reported

diabetes.

In addition to examining

beneficiaries with a CC Summary

indicator among those who self-reported

diabetes, and beneficiaries who selfreported diabetes among those with a

CC Summary indicator, beneficiaries

who had a CC Summary indicator but

did not self-report diabetes were also

examined. The rationale was to

determine if beneficiaries who had a CC

Summary indicator but did not selfFigure 4. NHIS Medicare beneficiaries with diabetes in Chronic Conditions Summary file

among those who self-reported diabetes, by metropolitan status and region
Percent 

100 

80 

60 

40 

20 

0 

Men Women Hispanic NonHispanic 

black 

NonHispanic 

white 

Aged 

65–74 

Aged 75 

and over 

Married Not 

married 

Ι 95% confidence inter val. 

NOTES:Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 6 in this repor t. 

SOURCES: CDC/NCHS, 20 05 National Health Inter view Sur vey (NHIS) linked to 2005 Medicare data. Percent 

0 

20 

40 

60 

80 

100 

Excellent, Fair or poor 0–1 2 or more Not obese Obese 

very good, or health self-reported self-reported

good health health health

conditions conditions 

Ι 95% conf idence inter val.
 

NOTES: Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 5 in this report. Health status was measured by asking the sur vey respondent
 

about his or her health or the health of a family member, “ Would you say the [person’s] health in general is excellent, very good, good, fair, or poor?” Obesity is body mass index 


greater than 30.
 

SOURCES: CDC/NCHS, 2005 National Health Inter view Survey (NHIS) linked to 20 05 Medicare data.
 

National Health Statistics Reports n Number 69 n November 1, 2013 Page 7

Figure 5. NHIS Medicare beneficiaries with diabetes in Chronic Conditions Summary file among those who self-reported diabetes, by

health status

Figure 6. NHIS Medicare beneficiaries who self-reported diabetes, among those with diabetes in Chronic Conditions Summary file, by

demographic characteristics
Page 8 National Health Statistics Reports n Number 69 n November 1, 2013

Ι 95% confidence interval. 

NOTES: Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 7 in this report. 

GED is General Educational Development high school equivalency diploma. Percentage of federal poverty level is 

based on family income and family size and composition using U.S. Census Bureau poverty thresholds; missing 

family income data were imputed. 

SOURCES: CDC/NCHS, 2005 National Health Interview Survey (NHIS) linked to 2005 Medicare data. 

0 

High school 

diploma, GED, 

or less than high 

school diploma 

Some college

 or more 

Below 100% 

of poverty 

level 

100%–199% 

of poverty 

level 

200% of 

poverty 

level or more 

60 

80 

100 

20 

40 

Figure 7. NHIS Medicare beneficiaries who self-reported diabetes, among those with

diabetes in Chronic Conditions Summary file, by education and poverty level Percent Ι 95% confidence interval. 

NOTES: Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 8 in this report. 

MSA is metropolitan statistical area; MSA status was determined using 2000 census data and 2000 standards for 

defining MSAs. 

SOURCES: CDC/NCHS, 2005 National Health Interview Survey (NHIS) linked to 2005 Medicare data. 

0 

20 

40 

60 

80 

100 

MSA Not MSA Northeast Midwest South West 

Figure 8. NHIS Medicare beneficiaries who self-reported diabetes, among those with

diabetes in Chronic Conditions Summary file, by metropolitan status and region

report were at increased risk of diabetes.

Beneficiaries who had a CC Summary

indicator but did not self-report diabetes

were more likely to be obese than

beneficiaries who did not have a CC

Summary indicator and did not selfreport diabetes (32.0% compared with

17.5%, p < 0.05).

Discussion

Among Medicare beneficiaries aged

65 and over, the prevalence of diabetes

was 27.8% using the CC Summary file.

In comparison, the prevalence in this

age group based on self-report from

NHIS was 20.0%. Other research based

on surveys report prevalence for this age

group of 17%–22% (6,9,10). The

Agency for Healthcare Research and

Quality (AHRQ) estimated the

prevalence of diabetes in the Medicare

population in 2008 to be 28.0%, based

on data from the Medicare Enrollment

Database for beneficiaries aged 65 and

over with at least 12 months of

continuous enrollment in Medicare Parts

A and B FFS (11); other recent

Medicare estimates range from 24% to

28% for 2005–2008 (11,12). Other

authors have found administrative

database estimates of diabetes

prevalence to be higher than selfreported estimates (7,8).

Overall, 93.0% of beneficiaries who

self-reported diabetes had a CC

Summary indicator for diabetes. This

number is higher than the estimate

reported from a recent study by Gorina

and Kramarow (29) based on records

from the NHANES I Epidemiologic

Followup study (1971–1992) linked to

Medicare claims from 1991 to 2000.

The Gorina and Kramarow (29) study

found that 68.6%–76.5% of previously

diagnosed and self-reported (based on

medical records and multiple years of

self-report) diabetes cases were

identified by Medicare claims (29).

However, the present report uses

2005 survey and administrative data,

and changes in diagnostic criteria,

increased awareness, and changes in
National Health Statistics Reports n Number 69 n November 1, 2013 Page 9 Percent 

0 

20 

40 

60 

80 

100 

Fair or poor 

health 

0–1 

self-reported

health

conditions 

2 or more 

self-reported

health

conditions 

Not obese Obese 

Ι 95% conf idence inter val. 

NOTES: Figures are based on Medicare beneficiaries aged 65 and over; for detailed data, see Table 9 in this report. Health status was measured by asking the 

sur vey respondent about his or her health or the health of a family member, “ Would you say the [person’s] health in general is excellent, ver y good, good, fair, or 

poor ?” Obesity is body mass index greater than 30. 

SOURCES: CDC/NCHS, 2005 National Health Inter view Survey (NHIS) linked to 2005 Medicare data. 

Excellent, 

very good, or 

good health 

Figure 9. NHIS Medicare beneficiaries who self-reported diabetes, among those with diabetes in the Chronic Conditions Summary file, by

health status

policies may have contributed to

differences in results. As prevalence has

increased and awareness has grown,

CMS policies have expanded covered

treatments for diabetes (30). As a result,

diabetes treatments are more likely to

generate Medicare claims and to be

picked up by the CC Summary

algorithm. Differences in the methods

and populations studied between the

current 2005 NHIS evaluation and the

Gorina and Kramarow study also exist.

The current study is based on a

nationally representative cross-sectional

sample of community-dwelling adults

aged 65 and over who were enrolled in

FFS in 2005. The Gorina and Kramarow

study was a longitudinal study with a

baseline of 1971–1975. That study

sample included participants born in

1935 or earlier who survived to 1991,

and did not exclude persons who had

been institutionalized during the

follow-up period.

In the current report, of those who

self-reported diabetes in NHIS, more

women than men and a higher

percentage of beneficiaries aged 75 and

over were identified as having diabetes

in the CC Summary file. Claims data

are for a specific time period (2005 in

this report), and diagnosis may have

occurred at any point prior to the

interview. Therefore, the presence of

diagnosis in the claim is subject to

utilization patterns. Women are more

likely than men to use health care

services (31). Research in adults

younger than age 65 has found that

women with diabetes have greater health

care utilization than men (32), and

women are more likely than men to use

inpatient and physician services in their

last years of life, although the

relationship may be confounded by

more women than men surviving to later

years of life (33). Differences by age

may be due to differences in health care

use, because a beneficiary must utilize

Medicare services to have claims count

toward the CC Summary algorithm, by

definition. For example, based on the

2010 NHIS, 13.6% of adults aged 65–74

had a hospitalization, compared with

18.3% of those aged 75–84, and 20.8%

of those aged 85 and over (34). When

looking at certain subpopulations of

survey respondents, especially men with

self-reported diabetes or respondents

younger than age 75 with self-reported

diabetes, consider that these groups are

less likely to have a CC Summary

indicator for diabetes despite the fact

that they have self-reported diabetes.

Outcomes based on administrative data,

such as cost estimates, also may

underestimate the burden of disease in

this subpopulation. This is especially

true if different patterns of health care

use are responsible for the lack of a CC

Summary indicator for those who

self-report diabetes.

Of the beneficiaries with an

indicator for diabetes in the CC

Summary file, only 67.0% self-reported

diabetes at the interview. The self-report
Page 10	 National Health Statistics Reports n Number 69 n November 1, 2013

percentage was higher for beneficiaries

under age 75 with a CC Summary

indicator, adults in regions other than

the Northeast with a CC Summary

indicator, adults in self-assessed poor

health, and adults with two or more

self-reported conditions with a CC

Summary indicator. Previous studies

have found that the presence of diabetes

in medical records tends to be higher

than self-report (7,9). This difference

may be due to respondents

misunderstanding survey questions or

their doctors’ diagnoses (8,35). In

addition, the respondent may not be

aware of his or her diagnosis at the time

of the survey (35). Although a medical

diagnosis of diabetes may have occurred

after the survey date, only 2.7% of the

beneficiaries in this study with an

indicator for diabetes in the CC

Summary file had a first recorded date

for diabetes in 2005. Alternatively,

physicians may code for diabetes when

ordering tests for diabetes; however, this

possibility could not be assessed (7).

When looking at certain subpopulations

of Medicare beneficiaries—such as

respondents from the Northeast, those

aged 65–74, and those with fewer

self-reported conditions or better

self-rated health—note that these

populations were less likely to selfreport diabetes, despite the fact that

administrative data identifies them with

diabetes. In studying these

subpopulations, researchers should

evaluate how potential overestimation

could affect their analyses and consider

using codes for conditions or treatments

related to diabetes in addition to CC

Summary identification.

Obesity is a risk factor for diabetes.

In this study, beneficiaries who had a

CC Summary indicator but did not

self-report diabetes were more likely to

also report a high BMI. The data do not

show whether the CC Summary

indicator is picking up at-risk

individuals who are being tested for

diabetes or high-risk individuals who

either do not know they have diabetes

or develop diabetes after the survey.

However, differences by obesity indicate

that the CC Summary indicator may be

an accurate representation of high-risk

individuals for diabetes, even if those

persons do not always report diabetes.

One potential limitation of this

study is that CMS does not receive

claims for MA enrollees (11). Although,

historically, MA beneficiaries have been

reported to be healthier and to have

lower mortality than traditional FFS

Medicare beneficiaries (15–17), recent

studies have found differences between

the two groups lessening (18,19). For

example, a recent analysis of NHANES

data linked to Medicare claims found no

differences in diagnosed diabetes

between FFS and MA enrollees (36).

Using the 2005 NHIS showed that

beneficiaries who were linked to

Medicare in 2005 but had no FFS

claims for diabetes during 1999–2005

were slightly older than those who had

FFS claims, but no difference was seen

in the number of comorbidities. A

sensitivity analysis examining only

beneficiaries with 12 months of FFS in

2005 reduced the sample size from

2,109 to 1,955; however, the percentage

of beneficiaries who self-reported

diabetes among those with a CC

Summary indicator, and the percentage

of those with a CC Summary indicator

among those who self-reported diabetes,

remained similar to the results presented

in this report. Another possible

limitation is that NHIS contains only

self-reported diagnosis of disease, and it

has been shown in other surveys that as

much as 46.2% of diabetes in the

population aged 65 and over is

undiagnosed (9). Other studies have also

reported that diabetes is more often

underreported than overreported (37).

The CC Summary indicator

identified more cases of diabetes than

self-report using the 2005 linked

NHIS–CMS data. Most beneficiaries

who self-reported diabetes in NHIS had

a CC Summary indicator, but not as

many people with a CC Summary

indicator self-reported diabetes. Some

participant characteristics were

associated with the concordance

between self-report and medical records.

Those interested in utilizing the

NHIS–Medicare linked files for

research, or in examining factors

associated with diabetes prevalence in

national data sources, should be aware

of the differences between self-report in

surveys and the Medicare CC Summary

algorithm based on encounter data, and

choose to use either self-report or CC

Summary file to represent diabetes

depending on their question of interest.

Linked data can be used to compare

different sources of information, or the

information from the two data sources

can be combined for a more complete

picture of diabetes from both

administrative and survey data. As more

survey years and new linkages with

Medicare become available, it will be

possible to compare the two sources in

greater detail.

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Page 12 National Health Statistics Reports n Number 69 n November 1, 2013

Table 1. Percentage with diabetes among Medicare beneficiaries aged 65 and over at NHIS

interview, by self-report or Chronic Condition Summary indicator

Weighted

Category with diabetes n percent CI

Self-reported diabetes in 2005 NHIS................ 420 20.0 18.0–22.2
 

2005 CC Summary indicator for those who self-reported

diabetes in 2005 NHIS........................ 390 93.1 89.9–95.4

CC Summary indicator for diabetes in 2005 Medicare

records ................................. 582 27.9 25.7–30.1

Self-reported diabetes in 2005 NHIS among those with a

2005 Medicare CC Summary indicator.............. 390 67.0 62.6–71.1

NOTES: Categories are not mutually exclusive. NHIS is National Health Interview Survey, and CC Summary is Medicare Chronic

Condition Summary file. CI is 95% confidence interval.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.

Table 2. Unweighted sample sizes and weighted percentages for Medicare beneficiaries

with diabetes in the CC Summary file, among beneficiaries aged 65 and over at NHIS

interview who self-reported diabetes, by demographic characteristics

Characteristic n Percent SE CI

Sex1

Men ................................. 168 87.4 2.6 81.3–91.7

Women ............................... 222 98.4 0.9 95.2–99.5

Age1 (years)

65–74 ................................ 212 90.5 2.2 85.2–94.0

75 and over............................. 178 96.8 1.3 92.8–98.6

Race and ethnicity

Hispanic ............................... 40 96.0 2.6 86.6–98.9

Non-Hispanic black ........................ 55 88.5 4.9 74.8–95.2

Non-Hispanic white ........................ 287 93.5 1.6 89.7–96.0

Marital status

Widowed, divorced, or not married .............. 234 94.2 1.5 90.3–96.6

Married or living with partner .................. 154 92.3 2.2 86.7–95.6

1

Probability (p < 0.05) based on chi-squared statistic for association.

NOTES: CC is chronic condition, and NHIS is National Health Interview Survey. SE is standard error. CI is 95% confidence

interval.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.

Table 3. Unweighted sample sizes and weighted percentages for Medicare beneficiaries

with diabetes in the CC Summary file, among beneficiaries aged 65 and over at NHIS

interview who self-reported diabetes, by education and poverty level

Characteristic n Percent SE CI

Education

High school diploma, GED, or less than a high school

diploma .............................. 142 94.6 2.1 88.8–97.5
 

Some college or more ...................... 246 92.3 1.8 88.0–95.2
 

Poverty level

Below 100% ............................ 71 97.7 2.1 86.0–99.7
 

100%–199% ............................ 133 96.6 1.6 91.7–98.7
 

200% or more ........................... 186 90.3 2.2 85.0–93.9
 

NOTES: CC is chronic condition, and NHIS is National Health Interview Survey. SE is standard error. CI is 95% confidence

interval. GED is General Educational Development high school equivalency diploma. Percentage of federal poverty level is based

on family income and family size and composition using U.S. Census Bureau poverty thresholds; missing family income data

were imputed.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.
National Health Statistics Reports n Number 69 n November 1, 2013 Page 13

Table 4. Unweighted sample sizes and weighted percentages for Medicare beneficiaries

with diabetes in the CC Summary file, among beneficiaries aged 65 and over at NHIS

interview who self-reported diabetes, by metropolitan residence and region

Characteristic n Percent SE CI

Location of residence

MSA............................... 283 92.3 1.7 88.1–95.1
 

Not MSA ............................ 103 95.6 2.0 89.6–98.2
 

Region
 

Northeast............................ 76 94.7 2.8 85.8–98.1
 

Midwest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 90.9 2.7 83.9–95.0
 

South .............................. 179 93.3 2.3 87.2–96.6
 

West. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 95.0 2.5 87.1–98.2
 

NOTES: CC is chronic condition, and NHIS is National Health Interview Survey. SE is standard error. CI is 95% confidence

interval. MSA is metropolitan statistical area; MSA status was determined using 2000 census data and 2000 standards for

defining MSAs.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.

Table 5. Unweighted sample sizes and weighted percentages for Medicare beneficiaries

with diabetes in the CC Summary file, among beneficiaries aged 65 and over at NHIS

interview who self-reported diabetes, by health status

Characteristic n Percent SE CI

Self-rated health

Good, very good, or excellent ............... 204 90.7 2.0 85.9–94.0
 

Fair or poor .......................... 186 95.9 1.8 90.5–98.3
 

Number of self-reported health conditions

0–1 ............................... 146 89.5 2.9 82.3–94.0
 

2 or more ........................... 244 95.1 1.4 91.5–97.2
 

Obesity

Not obese ........................... 217 93.4 1.8 89.0–96.1

Obese.............................. 152 91.9 2.5 85.4–95.6

NOTES: CC is chronic condition, and NHIS is National Health Interview Survey. SE is standard error. CI is 95% confidence

interval. Health status was measured by asking the survey respondent about his or her health or the health of a family member,

‘‘Would you say the [person’s] health in general is excellent, very good, good, fair, or poor?’’ Obesity is body mass index greater

than 30.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.

Table 6. Unweighted sample sizes and weighted percentages for Medicare beneficiaries

who self-reported diabetes, among beneficiaries aged 65 and over at NHIS interview with

a CC Summary indicator for diabetes, by demographic characteristics

Characteristic n Percent SE CI

Sex

Men ............................... 168 67.7 3.1 61.3–73.5

Women ............................. 222 66.4 3.0 60.1–72.1

Age1 (years)

65–74 .............................. 212 72.4 2.9 66.3–77.8

75 and over .......................... 178 61.1 3.3 54.5–67.4

Race

Hispanic ............................ 40 62.2 9.2 43.2–78.1

Non-Hispanic black...................... 55 65.4 6.0 53.0–76.0

Non-Hispanic white...................... 287 68.8 2.4 64.0–73.2

Marital status

Widowed, divorced, or not married ............ 234 64.0 3.0 57.9–69.8

Married or living with partner ................ 154 69.4 3.2 62.8–75.3

1

Probability (p < 0.05) based on chi-squared statistic for association.
 

NOTES: NHIS is National Health Interview Survey, and CC is chronic condition. SE is standard error. CI is 95% confidence
 

interval.
 

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.
 
Page 14 National Health Statistics Reports n Number 69 n November 1, 2013

Table 7. Unweighted sample sizes and weighted percentages for beneficiaries who

self-reported diabetes, among Medicare beneficiaries aged 65 and over at NHIS interview

with a CC Summary indicator for diabetes, by demographic characteristics

Characteristic n Percent SE CI

Education

High school diploma, GED, or less than a high

school diploma........................ 142 61.1 3.8 53.4–68.3
 

Some college or more .................... 246 70.0 2.7 64.6–75.1
 

Poverty level

Below 100% ......................... 81 66.1 6.0 53.5–76.8
 

100%–200% .......................... 139 65.6 4.0 57.4–73.0
 

200% or more ......................... 194 67.9 2.9 62.0–73.3
 

NOTES: NHIS is National Health Interview Survey, and CC is chronic condition. SE is standard error. CI is 95% confidence

interval. GED is General Educational Development high school equivalency diploma. Percentage of federal poverty level is based

on family income and family size and composition using U.S. Census Bureau poverty thresholds; missing family income data

were imputed.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.

Table 8. Unweighted sample sizes and weighted percentages for those who self-reported

diabetes, among Medicare beneficiaries aged 65 and over at NHIS interview with a CC

Summary indicator for diabetes, by metropolitan residence and region

Characteristic n Percent SE CI

Location of residence

MSA............................... 283 64.9 2.5 59.8–69.6
 

Not MSA ............................ 103 73.7 3.8 65.5–80.5
 

Region1

Northeast............................ 76 51.1 4.7 42.0–60.1
 

Midwest ............. ............. 86 71.9 4.4 62.5–79.7
 

South ............... ............... 179 71.5 3.0 65.3–77.0
 

West .............. .............. 49 70.8 6.5 56.6–81.9
 

1

Probability (p < 0.05) based on chi-squared statistic for association. The percentage for the Northeast was significantly different

from the percentages for all other regions (p < 0.01). There were no significant differences between other regions.

NOTES: NHIS is National Health Interview Survey, and CC is chronic condition. SE is standard error. CI is 95% confidence

interval. MSA is metropolitan statistical area; MSA status was determined using 2000 census data and 2000 standards for

defining MSAs.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.

Table 9. Unweighted sample sizes and weighted percentages for those who self-reported

diabetes, among Medicare beneficiaries aged 65 and over at NHIS interview with a CC

Summary indicator for diabetes, by health status

Characteristic n Percent SE CI

Self-rated health1

Good, very good, or excellent ............... 204 60.9 3.0 54.8–66.6
 

Fair or poor .......................... 186 74.9 2.9 68.7–80.2
 

Number of self-reported health conditions1

0–1 ............................... 146 59.9 3.7 52.5–66.9
 

2 or more ........................... 244 71.2 2.6 65.8–76.0
 

Obesity

Not obese ........................... 217 64.0 2.9 58.1–69.6
 

Obese.............................. 152 71.3 3.3 64.3–77.3
 

1

Probability (p < 0.05).

NOTES: NHIS is National Health Interview Survey, and CC is chronic condition. SE is standard error. CI is 95% confidence

interval. Health status was measured by asking the survey respondent about his or her health or the health of a family member,

‘‘Would you say the [person’s] health in general is excellent, very good, good, fair, or poor?’’ Obesity is body mass index greater

than 30.

SOURCE: CDC/NCHS, 2005 National Health Interview Survey linked to 2005 Medicare data.
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National Health Statistics Reports n Number 69 n November 1, 2013

Suggested citation

Day HR, Parker JD. Self-report of diabetes

and claims-based identification of diabetes

among Medicare beneficiaries. National health

statistics reports; no 69. Hyattsville, MD:

National Center for Health Statistics. 2013.

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public domain and may be reproduced or

copied without permission; citation as to

source, however, is appreciated.

National Center for Health Statistics

Charles J. Rothwell, M.S., Acting Director

Jennifer H. Madans, Ph.D., Associate Director

for Science

Office of Analysis and Epidemiology

Irma E. Arispe, Ph.D., Director

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DHHS Publication No. 2014–1250 • CS241740