Impact of income inequality on health in both rich and poor nations

A wide income gap between the most affluent and the worst off in society is closely associated with higher death rates worldwide, especially for younger adults, finds a study published on bmj.com as part of a global theme issue on poverty and human development.

Many studies have suggested that greater income inequality in a nation is associated with higher mortality rates, but most have focused on wealthier nations. However, it has recently been suggested that the effects of income inequality on health are of importance worldwide, not just in affluent nations. There is also some evidence that this effect is more pronounced at different ages, but currently this is not well understood.

So a research team, led by Danny Dorling at the University of Sheffield, set out to explore whether the apparent impact of income inequality on health, which has been demonstrated for wealthier nations, is replicated worldwide, and whether the impact varies by age. Richard Mitchell of the University of Glasgow and Jamie Pearce of the University of Canterbury (New Zealand) also worked on the research.

They analysed data on income inequality and mortality by age and sex for 126 countries of the world (94.4% of the world human population).

They confirm that the impact of income inequality on health is real and that it has a greater influence on mortality in wealthier countries between the ages of 15 and 29, and worldwide between the ages of 25 and 39.

The strength of this global relationship is reduced when countries in Africa are omitted from the analysis, suggesting that the worldwide result is partly a product of processes operating most strongly in this continent, not simply a reflection of those operating within wealthier countries, explain the authors.

These results show that high levels of inequality have a negative impact on population health in both rich and poor nations alike, they write. Although the direct mechanisms that operate are likely to be very different between such diverse places, there does not appear to be a beneficial impact of social inequality on health anywhere, they conclude.