Plan and operation of the NHANES II Mortality Study, 1992

The NHANES II Mortality Study is a prospective study of adult participants examined in the second National Health and Nutrition Examination Survey (NHANES II) conducted between 1976 and 1980. It was designed to investigate the association between factors measured at baseline and mortality. The methods used in the study are described and assessed in this report.

The vital status of NHANES II participants who were 30-75 years of age at their examination was ascertained after 12-16 years. Vital status was assessed by searching the National Death Index and the Social Security Administration Death Master File for deaths occurring in the United States. Causes of death were obtained from the National Center for Health Statistics Multiple Cause of Death file or death certificates. To assess how well mortality was ascertained, the survival of the cohort after 5 and 10 years was compared to that of the U.S. population during the same period.

As of December 31, 1992, 23.2 percent of the 9,250 cohort members were found to be deceased. The remaining 76.8 percent that were not found to be deceased may be assumed to be alive for analytic purposes. Cumulative survival probabilities for the cohort were generally higher than probabilities calculated from U.S. life table data. Although some differences were expected, these data suggest that after 10 years of follow-up using passive methods, mortality may have been under ascertained for the cohort. Discrepancies between the survival patterns for NHANES II cohort and U.S. vital statistics were larger for black than for white participants, indicating that ascertainment of mortality was poorer among black participants. Researchers using the NHANES II Mortality Study, 1992 data should be aware of these study limitations.