Income inequality and mortality: a multilevel prospective study of 521 248 individuals in 50 US statesy

Background Some of the most consistent evidence in favour of an association between income inequality and health has been among US states. However, in multilevel studies of mortality, only two out of five studies have reported a positive relationship with income inequality after adjustment for the compositional characteristics of the state’s inhabitants. In this study, we attempt to clarify these mixed results by analysing the relationship within age–sex groups and by applying a previously unused analytical method to a database that contains more deaths than any multilevel study to date. Methods The US National Longitudinal Mortality Study (NLMS) was used to model the relationship between income inequality in US states and mortality using both a novel and previously used methodologies that fall into the general framework of multilevel regression. We adjust age–sex specific models for nine socio-economic and demographic variables at the individual level and percentage black and region at the state level. Results The preponderance of evidence from this study suggests that 199