# Presentation: 463037

## National Center for Health Statistics	Record Linkage Program

**Christine S. Cox,**
** ****Chief, Special Projects Branch (SPB)**
** ****Office of Analysis & Epidemiology (OAE)**
**	****NCHS Data Users Conference**
**	****August 12, 2008**
**	****	****U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES**
**	****	****Centers for Disease Control and Prevention**
**	****	****National Center for Health Statistics**

**	**

## Overview

- _NCHS Record Linkage Program_
- Analytic Issues & Tools
- Comparative Analysis of Public vs Restricted Linked Mortality Files
- Accessing the Restricted-use Linked Data

## NCHS Record Linkage Program

- Links survey data with data collected from administrative records
- Designed to maximize the scientific value of the NCHS population-based surveys
- Examine factors that influence chronic disease, disability, health care utilization, morbidity, and mortality

## Why Do Linkage?

- Augments available information for major diseases, risk factors, and health service utilization
- Links exposures to outcomes
- Provides longitudinal component to survey data
- Reduces cost burden
- Re-contacting survey respondents for follow-up information can be expensive
- Increases accuracy and detail of data collected

## How Records are Linked

**How Records are Linked**

**Notes:**
Figure illustrates the process by which survey records are linked to administrative data.

## Research Potential of NCHS Linked Data

- Aging
- Risk factors for poor health outcomes (hip fractures, stroke, etc.)
- Disability
- Effects of chronic illness and obesity on disability and mortality
- Disparities
- Mortality patterns by race/ethnicity or socioeconomic status
- Health services
- Functional impairment and health care costs
- Methodologic Studies
- Validation of self-reports vs. administrative records
- Genetics
- Genetic variants and health outcomes

## Record Linkage Activities

- Mortality
- National Death Index
- Social Security Retirement and Disability
- Data from the Retirement, Survivors, Disability Insurance (RSDI) and Supplemental Security Income (SSI) programs
- Medicare enrollment and payments
- Enrollment and claims data

## NCHS Linked Mortality Data Files

**†**** ****Children included**

**Notes:**
Table listing completed mortality linkages and future mortality linkages by NCHS survey.  
NHIS 1986 through 2000, LSOA II, NHEFS, NHANES II, NHANES III and NNHS 1985 are currently linked to mortality data through 2000 or 2002. These surveys along with NHIS 2001 through 2004, NHANES 1999 through 2004 and NNHS 1995, 1997 and 2004 will be matched to mortality data through 2006 with an anticipated file completion date in 2009.

## Number of Deaths by Survey

- NHIS and LSOA II have mortality follow-up through 12/31/2002.
- NHEFS, NHANES II and III have mortality follow-up through 12/31/2000.

## Public-use Linked Mortality Files

- In 2007, released public-use files with a limited amount of perturbed data and reduced number of mortality variables
- NHIS 1986-2000
- NHANES III
- LSOA II
- Study comparing analyses from public-use and restricted-use linked mortality files demonstrated similar results
- Lochner et al. Am. J. Epidemiol. 2008 168: 336-344

## Mortality Data Elements

- Vital status
- Date of death or follow-up time
- Underlying cause of death
- Multiple cause of death*
- Age at death*
- Age last presumed alive*
- *only available on restricted-use files

## Research Potential of Linked Mortality Data

**Excess Deaths Associated with Underweight, Overweight, and Obesity**KM Flegal, BI Graubard, DF Williamson, MH Gail; *JAMA,* 2005;293:1861-1867.
**Living and Dying in the USA: **Behavioral, Health, and Social Differentials of Adult Mortality RG Rogers, CB Nam, RA Hummer; 2000.
**Suicide among male veterans: a prospective population-based study **MS Kaplan, N Huguet, BH McFarland, JT Newsom;  *J Epidemiol Community Health,* 2007; 61:619-624.

**Notes:**
Pictures 1-3: “ “

## NCHS Linked Medicare Data Files 

**NCHS Linked Medicare Data Files**** **

**Notes:**
Table listing completed Medicare linkages and future Medicare linkages by NCHS survey.
NHIS 1994 through 1998, LSOA II, NHEFS, NHANES II, and NHANES III are currently linked to 1991-2000 Medicare data. These surveys along with NHIS 1999 through 2005, NHANES 1999 through 2004 and NNHS 1997 and 2004 will be matched to 1999-2007 Medicare data in 2009.

## Medicare Linkage

- Medicare enrollment and claims data for the years 1991-2000
- Denominator file
- MEDPAR Inpatient hospitalization
- MEDPAR Skilled nursing facility (SNF)
- Hospital outpatient
- Home Health Agency (HHA)
- Hospice
- Carrier (physician/supplier Part B file)
- Durable Medical Equipment (DMERC)
- Next data release (1999-2007)
- All of the above files
- Chronic Conditions Warehouse
- Medicare Part D (Prescription Drugs)

## Summary Medicare Data File

- Summary Medicare Enrollment and Claims Files (SMEC) for 1991-2000
- Enrollment information from the Denominator file plus summary variables of claims and payments
- Variables modeled after MCBS cost and use files
- Total reimbursements per year
- Total number of claims by Medicare record type
- Summary of charges by Medicare record type
- Termination status & reason for termination
- Monthly HMO enrollment
- Medicare status code (i.e. Part A, B or both)

## Research Potential of Linked Medicare Data

- Examine risk factors for health conditions
- Examine reliability of survey data
- Compare survey reported Medicare enrollment to Medicare claims records
- Examine survey report of disability with program participation eligibility criteria
- Examine disparities in Medicare service utilization

## NCHS Linked SSA Data Files

**NCHS Linked SSA Data Files**

## Social Security Linkage

- Old Age, Survivor, & Disability Income
- Master Beneficiary Record (MBR), 1962 - 2003
- Program eligibility, benefit amount, payment status,            dual entitlement
- Payment History Update System (PHUS), 1984-2003
- Benefit payment amounts, including withholding information   for Medicare Part B premiums
- Supplemental Security Income
- Supplemental Security Record (SSR), 1974 - 2003
- Program eligibility, benefit information, and payment status

## Research Potential of Linked Social Security Data

- Examine reliability of survey information for SSA program participation and benefits
- Compare the health characteristics of early retirees (age 62) to those who postpone benefits
- Policy analysis using validated survey data
- Predicting the number of people who will become disabled based upon survey reported health conditions
- Determining whether current disability entitlement funding levels will be adequate as the population ages

## Future Linkage Activities

- Linkage of 1999-2004 Medicaid enrollment and claims data linked to 1999-2004 NHIS and NHANES
- NCHS series report comparing the mortality experience of the 1986-2000 National Health Interview Survey Participants with the U.S. population

## Overview

- NCHS Record Linkage Program
- _Analytic Issues & Tools_
- Comparative Analysis of Public vs Restricted Linked Mortality Files
- Accessing the Restricted-use Linked Data

## National Center for Health Statistics	Record Linkage ProgramAnalytic Issues and Tools

**	****Kimberly A. Lochner, SPB, OAE**
**	****NCHS Data Users Conference**
**	****August 12, 2008**
**	****	****U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES**
**	****	****Centers for Disease Control and Prevention**
**	****	****National Center for Health Statistics**

## Analytic Issues: Overview

- Linkage eligibility
- Linkage match status
- Combining survey years for the linked mortality files
- Changes in surveys or administrative data over time
- Issues with administrative data

## Mortality: Analytic Issues

- Eligibility status
- Sample weights
- Combining survey years for the linked mortality files
- Variance estimation
- Changes over time
- ICD-9 and ICD-10 codes
- Most of these issues apply only to the NHIS Linked Mortality Files

## Slide 25

**Notes:**
Picture 1: “ “

## Eligibility Status

- What determines eligibility for mortality follow-up?
- Age
- Non “adult” survey respondents are INELIGIBLE
- Future linkages will include children
- Sufficient data for matching
- Lack of identifying data makes you INELIGIBLE
- Drop INELIGIBLE survey respondents
- Variable indicating eligibility status on files

## Mortality Ineligibility:Lack of Matching Data (adults only)

## Eligibility Status

- Ineligibility a problem for NHIS
- Created new sample weights to account for ineligibility due to insufficient identifying data
- Original NHIS sample weights (WTFA)
- New NHIS sample weights (WGT_NEW)
- Only for core/person files
- Recommend using WGT_NEW

## Combining Survey Years

- NHIS linked mortality files cover two design periods (1986-1994 and 1995-2000)
- Follow guidelines on pooling NHIS years
- _[http://](http://www.cdc.gov/nchs/about/major/nhis/methods.htm)__[www.cdc.gov/nchs/about/major/nhis/methods.htm](http://www.cdc.gov/nchs/about/major/nhis/methods.htm)_
- Created new stratum and psu variables for NHIS Linked Mortality files to allow combining across NHIS design years

## Changes in Data Over Time

- ICD-9 (deaths 1979 – 1998) and ICD-10 (deaths 1999 to present) cover linked mortality files
- Use both sets of codes to obtain full counts of cause-specific deaths
- Individual codes (ICD_9REV, ICD_10REV)
- Recodes
- UCOD_282, (ICD-9)
- UCOD_72, (ICD-9)
- UCOD_34, (ICD-9)
- UCOD_358, (ICD-10)
- UCOD_113 - recodes deaths before 1998 using          ICD-10 guidelines
- Refer to vital statistics report on ICD comparability

## Medicare: Analytic Issues

- Eligibility status
- Eligible but not matched
- Death
- Linked but no Medicare data
- Managed care enrollment
- Non covered services
- Gaps in coverage
- Issues with Medicare data files
- See the NCHS-CMS linkage web page under “Analytic/Programming Support”

## Medicare Ineligible Population and Linkage Rates (65+ years)

## Ineligibles and Non-Matches

- Must be excluded from your sample
- Identify using the variable (CMS_MATCH) on the Feasibility Study Data files

## Identifying Deaths

- Survey participants interviewed before the availability of linked Medicare files could have died before 1991
- E.g. NHEFS, NHANES II or NHANES III respondents interviewed in Phase I (1988-91)
- Persons may die during study period and cease to have Medicare records
- Enrolled in Medicare in 1991 but died before 2000

## Identifying Deaths

- Survey respondents who died before 1991 (e.g. from NHANES) can be identified by merging mortality information from the Linked Mortality files
- Needed to create analytic sample
- Persons who died during 1991-2000 should no longer have Medicare records after date of death
- Look for a CMS date of death (DOD) on each of the Denominator or SMEC files (1991 to 2000)

## Linked but no Medicare data

- No denominator file because
- Loss of entitlement during 1991-2000
- Deceased prior to 1991
- CMS record keeping inconsistencies
- No claims data
- Not utilizing Medicare in 1991-2000
- No reimbursable claims
- CMS record keeping inconsistencies

## No Denominator Record

- Lack of denominator record can affect your analytic sample – why?
- Can’t determine managed care enrollment
- In general, managed care enrollees are excluded from sample (more on this to come)

## Managed Care Enrollment

- Medicare does not receive claims for beneficiaries enrolled in managed care plans (HMO)
- Do not have complete information on payments or services received
- Could miss health events that are being counted based upon submitted claims
- Complex issue. Refer to  ResDAC
- _[http://](http://www.resdac.umn.edu/)__[www.resdac.umn.edu](http://www.resdac.umn.edu/)__[/](http://www.resdac.umn.edu/)_

## How managed care enrollees affect your research depends upon your question...

- Studies on reimbursements/charges
- Option may be to exclude those with any managed care enrollment because you don’t have complete information on payments or services received
- Studies on health outcomes/events
- Option may be to exclude those with any managed care enrollment because you could miss events
- Option may be to censor observations at time of first HMO enrollment
- Other methods for addressing HMO enrollment possible depending upon research question

## Services not covered in Medicare 1991-2000 files

- Out-patient prescription drugs
- Routine physical and dental exams
- Dentures
- Eye glasses
- Out-of-pocket expenses for Medicare beneficiaries (e.g. deductibles, coinsurance)

## SSA: Analytic Issues

- Eligibility status
- Eligible but not matched
- Linked but no benefit history data
- Records are extracted from files designed for program administration - not for research

## SSA Ineligible Population and Linkage Rates

## Ineligibles and Non-Matches

- Must be excluded from your sample
- Identify using the variable (SSA_MATCH) on the Feasibility Study Data files

## Linked but no SSA Data

- Linkage is to SSA NUMIDENT file
- Linked to NUMIDENT file but may not be eligible for Social Security benefits
- Not age eligible for retirement
- Defer retirement benefits because working full-time
- Not eligible for Social Security

## Issues with Administrative Data

- Administrative data updates
- Payment history updates
- Previously denied claims may be overridden
- Changes to type of benefit status
- Individuals receiving disability (DI) switch to retirement (R) benefits at age 65 in RSDI program
- Complicated data
- File layouts are complex, e.g. each MBR record has 2 parts
- Calculation of benefits not straightforward, e.g. SSI benefits come from both federal and state programs

## Final Tips

- Read relevant documentation !!!
- Survey file layouts & detailed notes
- Linkage methodology reports
- Sample SAS & STATA input statements for public-use linked mortality files
- Analytic guidelines
- Consult basic program information
- CMS – _[http://](http://www.cms.gov/)__[www.cms.gov](http://www.cms.gov/)_
- ResDAC – _[http://](http://www.resdac.umn.edu/)__[www.resdac.umn.edu](http://www.resdac.umn.edu/)__[ ](http://www.resdac.umn.edu/)_(Medicare)
- SSA – _[http://](http://www.ssa.gov/)__[www.ssa.gov](http://www.ssa.gov/)__[ ](http://www.ssa.gov/)_and
- _[http://](http://www.ssa.gov/regulations/index.htm)__[www.ssa.gov/regulations/index.htm](http://www.ssa.gov/regulations/index.htm)_

## Final Tips

- Determine NCHS public-use files needed
- Determine RDC linked files needed
- Determine feasibility of research question based upon successfully linked respondents
- Public-use Feasibility Study Data files available indicating whether respondent was linked to Medicare or SSA data and whether there is a record on the various Medicare and/or SSA files
- Match status (SSA_MATCH & CMS_MATCH)

## Overview

- NCHS Record Linkage Program
- Analytic Issues & Tools
- _Comparative Analysis of Public vs Restricted Linked Mortality Files_
- Accessing the Restricted-use Linked Data

## National Center for Health Statistics	Record Linkage Program Comparative Analysis of the Public-use and Restricted-use Linked Mortality Files	Kimberly A. Lochner, SPB, OAE	NCHS Data Users Conference	August 12, 2008	U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICESCenters for Disease Control and PreventionNational Center for Health Statistics

## Objectives

- Present an overview of the newly* *available public-use linked mortality files
- National Health Interview Survey (NHIS) 1986 to 2000
- Third National Health a Nutrition Examination Survey (NHANES III)
- The Second Longitudinal Study of Aging (LSOA II)
- Demonstrate the analytic comparability between the public-use and restricted-use versions of the linked mortality files

## Background

- Mortality follow-up studies are a major focus of NCHS record linkage activities
- NCHS linked mortality files created in 2004 made available through NCHS Research Data Center (RDC)
- Protects confidentiality of survey participants
- May minimize access to highly utilized data sources

## Background

- NCHS plan for public-use linked mortality files included
- Releasing a reduced number of key mortality variables
- Perturbing date or cause of death for select records
- Determining that survey participants could not be reidentified
- Comparing the analytic utility of the public-use file to the restricted-use file

## Public-use Linked Mortality Files

- NHIS (1986 – 2000)
- Each NHIS year is nationally representative survey of the civilian non-institutionalized U.S. population
- Questionnaire content
- Basic socio-demographic characteristics
- Health conditions and utilization
- Health status, health care services, and behavior
- Mortality follow-up through December 2002

## Public-use Linked Mortality Files

- NHANES III (1988 – 1994)
- Includes survey and examination information designed to assess the health and nutritional status of U.S. adults and children.
- Study content
- Basic socio-demographic characteristics
- Medical and dental examinations
- Laboratory tests
- Environmental exposures
- Mortality follow-up through December 2000

## Public-use Linked Mortality Files

- LSOA II
- Prospective survey of persons 70 years of age and over at the time of their baseline interview (1994 NHIS)
- Follow-up interviews in 1997-98 and 1999-00
- Questionnaire content
- Basic socio-demographic characteristics
- Health conditions, functional health status and disability
- Health care utilization
- Mortality follow-up through December 2002

## Data Elements: NHIS Linked Mortality Files

- * MCOD flags only for diabetes, hypertension, and hip fracture
- **Available on the public-use NHIS survey data files

## Data Elements: NHANES III Linked Mortality Files

- * MCOD flags only for diabetes, hypertension, and hip fracture
- **Available on the public-use NHANESIII survey data files

**Notes:**
Table listing selected variables on the NHANES III linked mortality files by restricted-use or public-use version.

## Data Elements: LSOA II Linked Mortality Files

- * MCOD flags only for diabetes, hypertension, and hip fracture
- **Available on the public-use LSOA II survey data files

## Comparative Analyses

## Statistical Methods

- Compared mean follow-up times and distributions for select causes of death
- Compared the mortality risk for a standard set of socio-demographic covariates for all-cause as well as cause-specific mortality
- Cox proportional hazard models
- SUDAAN to take into account complex survey design

## Analytic Samples

- Eligible for mortality follow-up
- At least 25 years of age at the time of the survey interview
- Non-Hispanic white, non-Hispanic black, or Hispanic
- Non missing values for cause of death or other covariates

## Covariates

- Socio-demographic characteristics reported
- at time of interview and taken from public-use
- survey data files:
- Age
- Sex
- Race and ethnicity
- Educational attainment
- Marital status (except NHANES III)
- Region of the country (except NHANES III)

## Outcomes

- All-cause and cause-specific mortality
- Cause-specific deaths based on underlying cause of death from the ICD-10 113 grouped recode
- Duration of follow-up calculated from time of interview until death or censored at end of the follow-up period
- Restricted-use files use complete information on interview and death month, day, and year
- Public-use files use less detailed information on timing of death, some of which is perturbed
- NHIS/LSOA II: use interview year and death year only
- NHANES III: use person-time follow-up provided on the file

## NHIS Results

- Sample (n = 897,232)
- Deaths (n = 114,264)
- 11.8% weighted
- Follow-up (mean)
- Restricted-use = 8.6 years
- Public-use = 8.7 years

## NHIS Linked Mortality Files: Cause-specific Deaths

**Notes:**
Table listing the leading cause-specific deaths for adults aged 25 years and older in the 1986-2000 NHIS linked mortality files.

## NHIS Linked Mortality Files: Relative Hazards for All-Cause Mortality

- Note: Models also adjusted for marital status and region of the country.

## NHIS Linked Mortality Files: Relative Hazards for Homicide Mortality

- Note: Models are restricted to Non Hispanic Whites and Blacks (n = 802,307).
-           Models also adjusted for marital status and region of the country

## NHANES III Results

- Sample (n = 16,048)
- Deaths (n = 3,209)
- 12.1% weighted
- Follow-up (mean)
- Restricted-use = 104.1 months
- Public-use = 103.8 months

## NHANES III Linked Mortality Files: Cause-specific Deaths

**Notes:**
Table listing the leading cause-specific deaths for adults aged 25 years and older in the NHANES III linked mortality files.

## NHANES III Linked Mortality File: Relative Hazards for All-Cause Mortality

## NHANES III Linked Mortality File: Relative Hazards for Cerebrovascular Mortality

- Note: Models restricted to Non Hispanic Whites and Blacks (n = 11,985).

## LSOA II Results

- Sample (n = 8,867)
- Deaths (n = 3,671)
- 41.4% weighted
- Follow-up (mean)
- Restricted-use = 4.4 years
- Public-use = 4.4 years

## LSOA II Linked Mortality Files: Cause-specific Deaths

## LSOA II Linked Mortality File: Relative Hazards for All-Cause Mortality

- Note: Models also adjusted for marital status and region of the country.

**Notes:**
This table presents results from Cox proportional hazards models of all-cause mortality: one estimated from the public-use file and one estimated from the restricted-use file. 

## LSOA II Linked Mortality File: Relative Hazards for Cancer Mortality

- Note: Models restricted to Non Hispanic Whites (n = 7,586).
-           Models also adjusted for region of the country.

## Conclusions

- Public-use linked mortality files yield similar results as the restricted-use data
- Public-use and restricted-use files yield similar hazard ratios and confidence intervals, particularly for common causes of death
- Results for less common causes of death remain consistent, although there tends to be less agreement in the estimates

## Conclusions

- Caution is urged for analyses of very rare causes of death or small population subgroups
- Users of the public-use linked mortality files may request to verify their results through the NCHS Research Data Center

## Public-use Linked Mortality Files Can Be Downloaded

- _[http://www.cdc.gov/NCHS/r&d/nchs_datalinkage/data_linkage_activities.htm](http://www.cdc.gov/NCHS/r&d/nchs_datalinkage/data_linkage_activities.htm)_

## Acknowledgements

- American Journal of Epidemiology 2008 168(3):336-344
- SPB data linkage team
- Stephanie Bartee
- Jim Brittain
- Cordell Golden
- Donna Miller
- Gloria Wheatcroft

## Overview

- NCHS Record Linkage Program
- Analytic Issues & Tools
- Comparative Analysis of Public vs Restricted Linked Mortality Files
- _Accessing the Restricted-use Linked Data_

## NCHS Record Linkage Activities: Accessing Restricted Linked data at the NCHS Research Data CenterChristine CoxNCHS Data Users ConferenceAugust 12, 2008		U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES		Centers for Disease Control and Prevention		National Center for Health Statistics

## Why can’t you just give me the data?

- NCHS does not “own” the linked administrative data
- NCHS data confidentiality rules prohibit the release of potentially identifiable data – special considerations concerning the protection of linked data
- The RDC is the only option for access to restricted-use data files

## Research Data Center

- The RDC is a organizational unit located at NCHS headquarters in Hyattsville, MD
- Provides access to restricted use data files

## Restricted Data Files Include...

- Linked administrative data
- Medicare
- SSA
- Restricted-use linked mortality files
- Detailed geographic data or contextual data
- Census tract & State/county level data
- EPA air pollution data

## To gain access to NCHS restricted data user must:

Submit a research proposal
Sign an affidavit of confidentiality
Promise not to use any method to attempt to identify respondents

- Submit a research proposal
- Sign an affidavit of confidentiality
- Promise not to use any method to attempt to identify respondents

**What to Expect?**

## What to Expect?

- How long for a proposal to be reviewed?
- Usually within 2 weeks, if proposing to use public use survey data with the linked data
- Up to 1-2 months, if proposing to use non-public survey data with the linked data

## Access Methods

- Once approved, three methods to access restricted data
- on-site - use local computing resources in the NCHS RDC, Hyattsville, MD
- remote – submit programs electronically to be executed in the RDC with output returned by email
- Census RDC- access NCHS data using any one of the nine Census RDCs.
- For all methods of access, restricted data files remain in RDC and output is inspected for disclosure violations

## On-Site Access Method

- On-site Facilities
- Four user workstations-expandable as needed
- Pentium IV computers
- Windows XP
- SAS, STATA, SUDAAN, LIMDEP, SPSS, Watcom Fortran 77, & HLM
- No removable media
- Secure printer
- Open only during normal working hours
- RDC staff constructs necessary data files, including merged user data

## Remote Access Method

- RDC staff constructs necessary data files, including merged user data
- SAS programs only, including SAS callable SUDAAN (certain procedures and functions not allowed)
- Both submitted programs and output undergo a programmed disclosure limitation review
- Ability to submit analytical computer programs via email from anywhere in the world with access available 24hrs/day

## Census RDC Access Method

- 9 Census RDCs
- Los Angeles, Berkeley, Boston, Durham,
-    Ann Arbor, Ithaca, NYC, Chicago, & DC
- Separate Census research proposal is not needed
- May have to follow additional security requirements at Census Bureau facilities

## User Fees: Linked Data Access

**User Fees: Linked Data Access**

## Proposal Requirements

- Proposal is evaluated by review committee
- Review criteria
- Scientific and technical feasibility
- Availability of RDC resources
- Disclosure risk for restricted information
- The extent to which project is in accordance with the mission of NCHS
- Special note: NCHS does not try to determine if proposals are duplicative

## Proposal Requirements: Helpful Tips

- Be clear about research and data requirements (helps to determine feasibility of project)
- Clearly identify the sample to be included in the analytic file
- Provide data dictionaries for both
- Public-use data
- Restricted-use data
- Provide examples of expected output

## Visit the RDC at: http://www.cdc.gov/r&d/rdc.htm or email: rdca@cdc.gov

## Where to get Help?

- RDC website contains:
- Proposal Checklist
- Sample Proposal
- List of available restricted data files
- Detail on Census RDC locations and contact information
- FAQ’s regarding proposal review process, on-site procedures, area information and contact information
- Email: rdca@cdc.gov

## Questions?