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.