Racial disparities in adult all-cause and cause-specific mortality among us adults: mediating and moderating factors

Studies uncovering factors beyond socio-economic status (SES) that would explain racial and ethnic disparities in mortality are scarce.

Using prospective cohort data from the Third National Health and Nutrition Examination Survey (NHANES III), we examined all-cause and cause-specific mortality disparities by race, mediation through key factors and moderation by age (20-49 vs. 50+), sex and poverty status. Cox proportional hazards, discrete-time hazards and competing risk regression models were conducted (N = 16,573 participants, n = 4207 deaths, Median time = 170 months (1-217 months)).

Age, sex and poverty income ratio-adjusted hazard rates were higher among Non-Hispanic Blacks (NHBs) vs. Non-Hispanic Whites (NHW). Within the above-poverty young men stratum where this association was the strongest, the socio-demographic-adjusted HR = 2.59, p < 0.001 was only partially attenuated by SES and other factors (full model HR = 2.08, p = 0.003). Income, education, diet quality, allostatic load and self-rated health, were among key mediators explaining NHB vs. NHW disparity in mortality. The Hispanic paradox was observed consistently among women above poverty (young and old). NHBs had higher CVD-related mortality risk compared to NHW which was explained by factors beyond SES. Those factors did not explain excess risk among NHB for neoplasm-related death (fully adjusted HR = 1.41, 95 % CI: 1.02-2.75, p = 0.044). Moreover, those factors explained the lower risk of neoplasm-related death among MA compared to NHW, while CVD-related mortality risk became lower among MA compared to NHW upon multivariate adjustment.

In sum, racial/ethnic disparities in all-cause and cause-specific mortality (particularly cardiovascular and neoplasms) were partly explained by socio-demographic, SES, health-related and dietary factors, and differentially by age, sex and poverty strata.