Article Text
Abstract
Introduction Life expectancy is strongly related to national income, whether there is an additional contribution of income inequality is unclear. We examined the association of income inequality with mortality over historic time in a non-western population which has experienced uniquely rapid economic development.
Methods We used negative binomial regression to examine the association of neighbourhood level Gini, adjusted for age, sex and income, with all-cause and cause specific mortality rates in Hong Kong for an earlier (1976, 1981 and 1986) and later (1991, 1995, 2001 and 2006) period.
Results Neighbourhood Gini was not associated with all-cause mortality in the earlier period (incident rate ratio (IRR) 0.96, 95% CI 0.93 to 1.00 per 0.1 change in Gini) but was in the later period (IRR 1.25, 95% CI 1.20 to 1.29), adjusted for age, sex and absolute income, despite a consistent association with non-medical mortality in both periods (IRR 1.11, 95% CI 1.06 to 1.17 and 1.29, 1.21 to 1.37). In the later period Gini was associated with mortality from cardiovascular diseases, including ischaemic heart disease (IHD), and respiratory diseases, but not with mortality from cancer.
Conclusion The impact of income inequality on cardio-respiratory mortality emerged over a period of economic development. Whether there is any additional benefit beyond those provided by material conditions from re-distributing income is unclear and may be confined to some specific causes of death, such as non-medical mortality and IHD, for which specific interventions could be designed.