Codes and Frequencies
For persons aged 18 and older included in the 1986-2014 NHIS samples and sample adults aged 18 and older included in the 2015-2018 NHIS samples who provided sufficient data for linking (MORTELIG) and whose final vital status was judged deceased (MORTSTAT) as of December 31, 2019, MORTUCODLD reports the leading underlying cause of death. For more information about the methodology to link NHIS records to the NDI, please see the NCHS report on the NHIS-NDI linkage methods and analytic considerations. For survey respondents in the 2005 or later surveys and decedents who died after December 2006, MORTUCODLD is the most detailed information available on the linked NHIS-NDI public use files about underlying cause of death. For access to the detailed cause of death codes available on the linked NHIS-NDI restricted access files, see documentation on the restricted version of the NHIS Linked Mortality Files.
MORTUCODLD is a recode created by NCHS to classify underlying cause of death into 10 categories. Deaths that occurred prior to 1999 are coded based on the 9th revision of the International Statistical Classification of Diseases, Injuries, and Causes of Death (ICD-9). Deaths that occurred from 1999 forward were coded based on the 10th revision of the International Statistical Classification of Diseases, Injuries, and Causes of Death (ICD-10). In sample years 2015 forward, eligible respondents are limited to a single sample adult per household. Because of the smaller sample size, NCHS has grouped people with MORTUCODLD codes of 5-9 into code 10 (All other causes - residual) to lower the risk of respondent identification. Please see the Public-use Linked Mortality File Readme for information about these codes.
MORTUCODLD is one of a set of mortality variables released by the National Center for Health Statistics (NCHS) as part of the 2019 Linked Mortality File (LMF) update. The 2019 LMF includes mortality information for participants in the 1986-2018 NHIS samples with mortality follow up in the NDI through December 31, 2019. For more information on the LMF, including which variables it offers and the appropriate sampling weights to use when analyzing the mortality data, see the description tab of MORTELIG.
For a list of all mortality variables from the LMF included in the IPUMS NHIS, please refer to the MORTELIG variable description.
Aside from universe changes and the change from ICD-9 to ICD-10 codes to classify cause of death, MORTUCODLD is largely comparable over time. Between 1986 and 2014, the universe for MORTUCODLD included all adults 18 and older. In 2015 and later years, the MORTUCODLD universe narrowed to only persons selected to be the sample adult and some codes are reassigned. As noted above, deaths occurring prior to 1999 are based on the 9th revision of the International Statistical Classification of Diseases, Injuries, and Causes of Death (ICD-9); deaths occurring from 1999 forward are coded based on the 10th revision (ICD-10).
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 age 18+ eligible for mortality follow-up, assumed dead, and whose assumed cause of death was not unknown.
- 2015-2018: Sample adults age 18+ eligible for mortality follow-up, assumed dead, and whose assumed cause of death was not unknown.