Socio-economic inequalities in mortality persist into old age in New Zealand: study of all 65 years plus, 2001-04

A number of studies have explored the relationship between socio-economic status and mortality, although these have mostly been based on the working-age population, despite the fact that the burden of mortality is highest in older people. Using Poisson regression on linked New Zealand census and mortality data (2001-04, 1.3 million person years) with a comprehensive set of socio-economic indicators (education, income, car access, housing tenure, neighourhood deprivation), we examined the association of socio-economic characteristics and older adult mortality (65 + years) in New Zealand. We found that socio-economic mortality gradients persist into old age. Substantial relative risks of mortality were observed for all socio-economic factors, except housing tenure. Most relative risk associations decreased in strength with ageing [e.g. most deprived compared to least deprived rate ratio for males reducing from 1.40 (95% confidence interval (CI) 1.28-1.53) for 65-74-year-olds to 1.13 (CI 1.00-1.28) for 85 +-year-olds], except for income and education among women where the rate ratios changed little with increasing age. This suggests individual-level measures of socio-economic status are more closely related to mortality in older women than older men. Comparing across genders, the only statistically significantly different association between men and women was for a weaker association for women for car access.