Background The ‘inequality hypothesis’ proposes that higher levels of societal income inequality have a detrimental effect on both physical and mental health. Previous studies have provided only mixed support for this hypothesis, particularly among older people. However, by using only contemporary income inequality estimates, or estimates from a single lag period, the majority of previous studies have not accounted for people’s continued exposure to income inequality over the long-term. In this study, we addressed this problem by examining the association between older people’s experience of inequality over an extended period and their subsequent health.

Methods The data for this project were taken from three comparable nationally representative surveys (covering 16 countries) of the health and circumstances of older people; the English Longitudinal Study of Ageing, the Survey of Health and Retirement in Europe, and the U.S. Health and Retirement Study. Standardised estimates of national income inequality from 1960–2006 were taken from the Standardised World Income Inequality Database. We used multilevel regression methods to model the association between average inequality over this period and four measures of individual health: Objectively measured grip strength and lung function, and subjectively reported physical limitation and depressive symptoms.

Results We found that, after adjusting for individual and country-level covariates, exposure to higher average levels of inequality over the long-term was significantly negatively related to objectively measured grip strength and lung function, but unrelated to self-reported physical limitations or depressive symptoms.

Conclusion Our results show that long-term exposure to income inequality may indeed be detrimental to the physical health of older people. However, we found no evidence of an effect of inequality on subjectively reported limitations or depressive symptoms. This may be an effect of unmeasured covariates, or it may be due to the greater accuracy afforded by the objective health measures. To our knowledge this study represents the first direct evidence linking experience of inequality to the health of older people which has made use of either objective measures of health at the individual level, or a measure of inequality exposure over the long term.