Task 1: How the NHANES data are linked to Medicare enrollment and claims data

Data for survey respondents who were considered linkage eligible were sent to CMS to match to the CMS Denominator file for the specific years of interest. The range of years of NHANES and Medicare data that are linked are described in Course 1, Module 3, Task 2 “NHANES-CMS Linked Data Years of Availability”. The NHANES file used for matching did not contain the NHANES participants’ public-use ID.

NHANES linkage eligible respondents were linked with their Medicare data using the following individual identifiers:

• Social Security Number (SSN),
• Date of birth (month, day, year), and
• Sex

To be considered a successful match, the NHANES respondent’s record needed to match exactly to the CMS Denominator File for all three items listed above. CMS extracted data from each of the Medicare files for the specific years of linkage for those records that were successfully matched to the continuous NHANES respondents.  

It should be noted that survey participants who died in the time frame between the survey and the linkage interval were eligible for linkage if they had sufficient personal identifier information and had not refused to provide their SSN or HIC number. Non-matches include those participants eligible for linkage that were not enrolled in Medicare, as well as those not successfully matched to the CMS Denominator file for the specific years.

A more thorough discussion on the linkage process for Medicare may be found in the report Linkages between Survey Data from the National Center for Health Statistics and Medicare Program Data from the Centers for Medicare and Medicaid Services. A link to the report is located in the Resources section.

Resources

• Linkages between Survey Data from the National Center for Health Statistics and Medicare Program Data from the Centers for Medicare and Medicaid Services