State-level income inequality and individual mortality risk: A prospective, multilevel study

Objectives. Previous studies have linked state-level income inequality to m ortality rates. However, it has been questioned whether the relationship is independent of individual-level income. The present study tests whether st ate-level income inequality is related to individual mortality risk, after adjustment for individual-level characteristics. Methods, In this prospective, multilevel study design, the vital status of National Health Interview Survey (NHIS) respondents was ascertained by link age to the National Death Index, with additional linkage of state-level dat a to individuals in the NHIS. The analysis included data for 546 888 person s, with 19 379 deaths over the 8-year follow-up period. The Gini coefficien t was used as the measure of income inequality. Results. Individuals living in high-income-inequality states were at increa sed risk of mortality (relative risk= 1.12; 95% confidence interval = 1.04, 1-19) compared with individuals living in low-income-inequality states. In stratified analyses, significant effects of state income inequality on mor tality risk were found, primarily for near-poor Whites. Conclusions. State-level income inequality appears to exert a contextual ef fect on mortality risk, after income is adjusted for, providing further evi dence that the distribution of income is important for health.