Does migration between differently deprived areas at different ages lead to health inequalities?

The notion that mortality inequalities between differently deprived areas vary by age is logical since not all causes of death increase in risk with age and not all causes of death are related to the gradient of deprivation. In addition to the cause–age and cause–deprivation relationships, population migration may redistribute the population such that the health–deprivation relationship varies by age. We calculate cross-sectional all cause mortality and self-reported limiting long-term illness (LLTI) rate ratios of most to least deprived areas to demonstrate inequalities at different ages. We use longitudinal data to investigate whether there are changes in the distribution of cohorts between differently deprived areas over time and whether gradients of LLTI with deprivation also change. We find similar deprivation inequalities by age for all cause mortality and self-reported health with less inequality for young adults and the elderly but the greatest inequalities during mid life. Over time there are systematic movements of cohorts between differently deprived areas and associated increases and decreases in the gradient of LLTI across deprivation. It seems likely that population migration does influence inequalities by age. Further work should investigate whether the situation exists for other morbidities and, to better inform public health policy, whether restricting summary measures of area health to ages between 30 and 60 when inequalities are greatest will highlight between area differences.