About NCHS Data Linkage

NCHS data linkage program

The National Center for Health Statistics (NCHS) links data from several of the center's surveys to other government agencies' administrative data. Linking data from several sources maximizes the scientific value of NCHS's population-based and provider surveys. It can provide a more complete, accurate picture of population trends and needs.

Linked data files enable researchers to examine the factors that influence—

• Disability
• Chronic disease
• Healthcare use
• Morbidity (disease)
• Mortality (death)

Data sources

Visit the following NCHS Data Linkage pages to find details about the data, data files, and more—

• National Death Index (NDI)
• Centers for Medicare and Medicaid Services (CMS)
  • Medicare
  • Medicaid/CHIP
• United States Renal Data System
• Department of Housing and Urban Development
• Department of Veterans Affairs

NCHS has released its first fully synthetic linked data file and created a verification process so that researchers can confirm synthetic data results against the original data.

Some NCHS linked data resources are no longer routinely updated but are still available for research use. Access the past linked data project materials in the .

Geocoded and contextual data

NCHS collects geographic information such as state, county, and other geographical units for its survey participants and for vital records (birth and death certificates). NCHS codes the geographic information into standardized codes (geocodes) that are used across the federal government.

Geocoded data are available from many sources. Information about what geographic variables, or geocodes, are available for each NCHS data system is available on the Research Data Center's Geographic Variables webpage.

NCHS geocoded data are restricted-use data because they contain sensitive information about where people live. This increases reidentification risk. Applications to analyze or use NCHS geocoded data to merge with external data are submitted using a Standard Application Process.

What's new

• Release of Restricted-use Linked Mortality Files for the 2019 and 2020 National Hospital Care Survey
• NCHS public-use synthetic linked data
• Release of 2021 National Ambulatory Medical Care Survey Health Center Component Linked to Department of Housing and Urban Development Housing Assistance Program Data
• Release of Restricted-use Linked Mortality Files for the 2021 National Ambulatory Medical Care Survey Health Center Component
• Additional linked CMS Medicare data release
• (2024)