Evaluation of mortality data for older Mexican Americans: implications for the Hispanic paradox

The authors evaluated underascertainment bias in Hispanic mortality rates from population surveys linked to the US National Death Index (NDI). They compared vital status through 7 years ascertained from an NDI search and from active follow-up for 2,886 Mexican-American subjects, aged >/=65 years at baseline in 1993-1994, from the Hispanic Established Populations for Epidemiologic Studies of the Elderly (EPESE). Estimates of NDI underascertainment were applied to mortality rate ratios for 66,667 older Mexican Americans and non-Hispanic Whites from the 1986-1994 National Health Interview Surveys linked to the NDI. The NDI and active follow-up agreed on vital status for 91.2% of Hispanic EPESE subjects. The NDI did not identify 177 deaths (20.7%) reported by proxies. Underascertainment was greater for women and when stratified by age and nativity. The ratios of proxy-reported to NDI mortality rates were 1.31 (95% confidence interval (CI): 1.06, 1.62) for immigrant men and 1.65 (95% CI: 1.32, 2.08) for immigrant women. Before adjustment, National Health Interview Surveys-NDI age-standardized mortality rate ratios comparing Mexican Americans with non-Hispanic Whites were 0.77 (95% CI: 0.65, 0.92) for men and 0.92 (95% CI: 0.77, 1.09) for women but were 0.84 and 1.18, respectively, with adjustment for underascertainment. Findings suggest that NDI-based Hispanic mortality rates may be understated.