Community-level income inequality and mortality in Québec, Canada

Objectives: Evidence of the association between income inequality and mortality for small rather than large areas is conflicting. This study evaluated community-level income inequality in relation to age- and cause-specific mortality. Study design: Ecological analysis. Methods: Mortality data were extracted from the Québec, Canada registry for 1999-2003. For Québec communities (n = 143), directly standardized mortality rates were calculated for all-cause (overall, working-age and post-working-age), suicide, alcohol, tobacco and cardiovascular mortality. Using 2001 Canada Census data, the tertiles of income inequality measured as the decile ratio, coefficient of variation and median share were calculated. The relative risk (RR) of death was determined using Poisson regression, accounting for median community income, family structure and rural-urban area. Results: Income inequality was most strongly associated with alcohol-related mortality (RR_{CoefficientVariation} 0.85, 95% confidence interval 0.77-0.94), followed by statistically significant but weaker inverse associations with tobacco-related and age-specific all-cause mortality. Conclusions: Income inequality in Québec communities is inversely associated with mortality outcomes, particularly alcohol-related mortality. These associations contrast with positive or null associations observed in studies of larger US and Canadian metropolitan areas, respectively. Community-level studies accounting for individual-level covariates are necessary to clarify the relationship between income inequality and mortality.