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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Center for Health Statistics. National Health Interview Survey (NHIS) Linked Mortality File Overview. Christine S. Cox Special Assistant for Record Linkage.

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National Health Interview Survey (NHIS) Linked Mortality File Overview

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Centers for Disease Control and Prevention

National Center for Health Statistics

National Health Interview Survey (NHIS) Linked Mortality File Overview

Christine S. Cox

Special Assistant for Record Linkage

Bryan Sayer, Donna Miller, Jim Brittain

national health interview survey nhis
National Health Interview Survey(NHIS)
  • Nationally representative household based survey of the civilian non-institutionalized U.S. population.
  • Conducted continously
  • Surveys approximately 43,000 households per year for a total person sample of about 100,000
  • Collects information on health conditions and utilization, access to care and health insurance coverage, along with other varying special topics of interest
  • Survey design materials, questionnaires, and analytic reports available from the NCHS web site.
national death index
National Death Index
  • A centralized electronic data base containing death information from U.S. death certificates  
  • Available by application for statistical research only
  • Users submit records containing study participant data to attempt to match to correct death record
  • Each death record contains: demographic characteristics of the decedent, state of death, underlying/multiple causes of death
  • Current Coverage: 1979-2002
  • NDI webpage:
nhis ndi linkage
NHIS-NDI Linkage
  • Conducting NDI data linkage is both a scientifically valuable and cost effective data collection activity.
  • Provides the opportunity to conduct a wide variety of mortality outcome studies analyzing NHIS questionnaire data on health conditions, insurance coverage, health behaviors and other risk factors
    • Example: breast cancer death rates among uninsured vs. insured women
previous vs current nhis linked mortality files
Previous vs. current NHIS Linked Mortality files
  • Previous NHIS Mortality Data Files
    • 1986-1994 NHIS Mortality Data through 1995
    • 1986-1994 NHIS Mortality Data through 1997
  • Current NHIS Linked Mortality File
    • 1986-2000 NHIS Mortality Data through 2002
nhis ndi mortality linkage methodology
NHIS – NDI Mortality Linkage Methodology
  • Based on a probabilistic match to the NDI
  • No death certificates were collected for verification purposes
  • Calibration study was conducted
  • Best plausible NDI match record provided on user file (Definite non-matches eliminated)
  • Final match status assigned
    • Presumed Dead, Presumed Alive, Ineligible
ineligible population
Ineligible Population
  • All NHIS respondents under age 18 are not eligible for mortality follow-up
  • All adult NHIS respondents who do not meet the minimum criteria set by NDI are defined as ineligible.
    • SSN, sex, m/d/y of birth present
    • Last name, first initial, month of birth, year of birth present
    • Last name, first initial, SSN present
  • Analysts should treat ineligibles as lost to follow-up
    • New sample weights developed
total nhis deaths by survey year
Total NHIS Deaths By Survey Year

1The 1986 and 1996 NHIS were fielded with a reduced sample.

nhis linked mortality file access
NHIS Linked Mortality File Access

NCHS Research Data Center (RDC)

Purpose –

  • To provide access to restricted data files which data users would not be able to otherwise access

Accessibility –

  • On-site access – NCHS, Hyattsville, MD
  • Off-site access - User’s remote location
user procedures
User Procedures

To gain access to NCHS restricted data users must:

  • Submit a research proposal and receive approval
  • Sign an affidavit of confidentiality and promise not to use any method to attempt to identify respondents
  • Submit data files to be linked with RDC data ahead of time – all linking is conducted by RDC staff
  • Subject all output and/or materials removed from the RDC to a disclosure limitation review
  • Pay a user’s fee that will be estimated prior to proposal approval
rdc contact information
RDC Contact Information

For general Questions/Comments

Email: Phone: (301)458-4732

For On-site Info: Negasi Beyene

Email: Phone: (301)458-4097

For Remote Access Info: Vijay Gambhir Phone: (301)458-4226

file structure
File Structure

A standard linked mortality file has been developed to assist RDC users:

  • All variables on the standard will be linked to approved researcher’s analytic file (no need to specify variables of interest)
  • Additional variables available by special approval only
    • Geography
    • Occupation & Industry
linked mortality file structure
Linked Mortality File Structure
  • Separate mortality data file for each NHIS survey year containing the total number of NHIS respondents for that survey year
  • File documentation will be available for download on the NCHS Data Linkage web page (
  • Send email queries to (
    • Include NHIS Linked Mortality File in Subject line if possible for quicker routing
standard nhis linked mortality file
Standard NHIS Linked Mortality File
  • NHIS Public Use ID
  • Eligibility Status
  • NDI match results
  • Date of Birth and Death (to calculate survival period)
  • Underlying and Multiple Causes of Death
  • Sample weights
nhis survival period
NHIS Survival period

Decedents (Presumed Dead)

  • End date = date of death

Survivors (Presumed Alive)

  • End date = December 31, 2002
  • Some respondents appear to have very advanced ages (Dec. 31, 2002 – Date of birth)
  • Analysts should consider reassigning these cases as lost-to-followup (otherwise immortal) or review the NDI results to see if a “close to match” NDI record exists that could be reassigned as deceased
cause of death codes underlying cause of death recode groups
ICD-9 (1986-1998)




ICD-10 (1999-2002)

358 (all years coded)

113 (all years coded)


Cause of death codesUnderlying cause of death recode groups