While this tutorial’s focus is on using NHANES data that are linked to Medicare and Medicaid enrollment and claims data from CMS, you may find it useful to include mortality data in your analysis to gain additional information about the respondent. In addition to the CMS linked data files, NCHS surveys are also linked to the National Death Index (NDI). The linked mortality files contain date and cause of death information for NHANES decedents.
The NHANES Mortality Data Linkage webpages provide a complete overview of the linked mortality files, how to access the files, and description of the matching methodology. A more detailed description of how to use death data in the CMS files and linked mortality files is found in Course 4, Analytic Considerations and Limitations.
CMS files also contain the date of death but not the cause of death. The Medicare Denominator File and the MAX PS File include information on date of death if it occurred during the calendar year of the data file. The source of information on dates of death from these CMS data files comes from SSA records, rather than the NDI.
Death information is occasionally misreported to CMS. This erroneous information is not corrected by CMS; however, these cases can be identified as they continue to be eligible for benefits in later years or they have new death information recorded in a later file. You should use extra caution in analyzing CMS death information to ensure that deaths are not over-counted. In addition, the actual date of death information is occasionally misreported to CMS. Cases can be identified by examining the variable, “Valid Date of Death Switch”, where a value of “V” indicates that CMS has validated the actual date the beneficiary died, whereas a “blank” indicates that it was not validated. In the event that the date of death is not validated, CMS assigns the date of death as the last day of the month.
No attempt has been made to reconcile inconsistent death information from CMS. RDC research proposals that intend to analyze mortality outcomes should utilize death information from both the CMS data and the NHANES Linked Mortality Files.