Research: Income inequality, mortality, and self rated health: meta-analysis of multilevel studies
Author(s)/Editor(s): Naoki Kondo, Grace Sembajwe, Ichiro Kawachi, van Dam R M, Subramanian S V, Zentaro Yamagata
Publication date: 2009
To provide quantitative evaluations on the association between income inequality and health. Design Random effects meta-analyses, calculating the overall relative risk for subsequent mortality among prospective cohort studies and the overall odds ratio for poor self rated health among cross sectional studies.
The results suggest a modest adverse effect of income inequality on health, although the population impact might be larger if the association is truly causal. The results also support the threshold effect hypothesis, which posits the existence of a threshold of income inequality beyond which adverse impacts on health begin to emerge. The findings need to be interpreted with caution given the heterogeneity between studies, as well as the attenuation of the risk estimates in analyses that attempted to control for the unmeasured characteristics of areas with high levels of income inequality.