Codes and Frequencies
For all persons in the 1986-2014 NHIS samples and sample adults and sample children in the 2015-2018 NHIS samples, MORTELIG indicates whether they were eligible for follow-up through December 31, 2019 in the Linked Mortality File (LMF) by linkage to the National Death Index (NDI). Only persons (or sample adults, starting in 2015) who were 18 and older at the time of interview and who provided sufficient data were eligible for linkage to the NDI and inclusion in the public use files (IPUMS NHIS code 1 in MORTELIG). Linked mortality data for children (IPUMS NHIS code 2) are not available from the NHIS public use files; researchers interested in these data or in material with additional detail should review the documentation for the restricted access NHIS Linked Mortality Files. Adults with insufficient data for matching (IPUMS NHIS code 3) could not be linked to the NDI to create mortality variables.
LMF Variables in the Public Use Update
The following variables were included in the 2019 LMF update:
- MORTDIAB: Diabetes flag from multiple cause of death (MCOD)
- MORTDODQ: Quarter of death
- MORTDODY: Year of death
- MORTELIG: Eligibility status for mortality follow-up
- MORTHYPR: Hypertension flag from multiple cause of death (MCOD)
- MORTSTAT: Final mortality status
- MORTUCODLD: Leading underlying cause of death (ICD-10)
- MORTWT: Weight adjusted for ineligible respondents in mortality analysis
- MORTWTSA: Sample adult weight adjusted for ineligible respondents in mortality analysis
Because adult survey participants who provided insufficient data for linking may differ from those who provided enough data for linking, ignoring the ineligible adult respondents (IPUMS NHIS code 3 in MORTELIG) could lead to biased mortality analysis. To correct this bias, NCHS developed eligibility-adjusted weights for use with the LMF update variables: MORTWT, available for 1986-2014, for use with variables from the NHIS person files, and MORTWTSA, available for 1997-2018, for use with variables from the sample adult files. When analyzing NHIS variables from the person files in conjunction with mortality variables, users should employ MORTWT (rather than the standard person weight, PERWEIGHT). When analyzing variables from the sample adult files in conjunction with mortality variables, users should employ MORTWTSA (rather than the standard sample weight, SAMPWEIGHT). In the 2015 and later NHIS samples, only sample adults are eligible for linkage to the NDI; analyses of the mortality data from these samples should employ MORTWTSA.
Aside from changes in the universe over time, MORTELIG is completely comparable across years. Between 1986 and 2014, the universe for MORTELIG included all persons. In 2015 and later years, the MORTELIG universe narrowed to only persons selected to be the sample adult or sample child.
For an overview of the LMF data, NHIS-NDI linkage activities, and more information about the public use LMF offered through IPUMS NHIS, please refer to our user note on the Linked Mortality File.
- 1986-2014: All persons.
- 2015-2018: All sample adults and sample children.