Income Inequality and Cause-Specific Mortality During Economic Development

PurposeLife expectancy is strongly related to national income, whether there is an additional contribution of income inequality is unclear.MethodsWe used negative binomial regression to examine the association of neighborhood-level Gini, adjusted for age, sex, and income, with mortality rates in Hong Kong from 1976 to 2006.ResultsThe association of neighborhood Gini with all-cause mortality varied over time (p-value for interaction < .01). Neighborhood Gini was positively associated with nonmedical mortality in 1976 to 1986; incident rate ratio (IRR) 1.09, 95% confidence interval (95% CI) 1.02−1.16 per 0.1 change and in 1991 to 2006, IRR 1.24, 95% CI 1.13−1.36, adjusted for age, sex and absolute income. Similarly adjusted, Gini was not associated with all-cause mortality in 1976 to 1986 (IRR 0.96, 95% CI 0.93−1.00) but was in 1991 to 2006 (IRR 1.25, 95% CI 1.20−1.29), when Gini was also positively associated with death from cardiovascular diseases, respiratory diseases and some cancers.ConclusionsIndependent of income, income inequality was positively associated with nonmedical mortality rates at a low level of spatial aggregation, indicating the consistent harms of social disharmony. However, the impact on medical mortality was less consistent, suggesting the relevance of contextual factors.