Income differences in stroke mortality: A 12-year follow-up study of the Swedish working population

Aims: This study explored the association between income and stroke mortality in the total working population in Sweden and examined whether the associations differ by gender or for stroke subtypes intracerebral haemorrhage (ICH) or brain infarction (BI). Methods: This was a register-based study among nearly 3 million working women and men (30-64 years in 1990) with a 12-year follow up (1991-2002) for mortality from stroke (4886 deaths). Income was measured as annual registered income from work in 1990. Gender-specific Cox regressions were applied with adjustments for sociodemographic covariates. Results: The age-adjusted hazard ratio (95% confidence interval) of lowest versus highest income quartile was 1.80 (1.48-2.19) for any stroke, 1.68 (1.29-2.17) for ICH and 2.23 (1.53-3.22) for BI in women, and the corresponding figures for men were 2.12 (1.92-2.34), 2.02 (1.77-2.31), and 2.09 (1.77-2.46). Adjustment for covariates attenuated these associations to 1.69 (1.33-2.15) for any stroke and 1.56 (1.14-2.14) for ICH in women and to 1.98 (1.74-2.24) for any stroke and 1.77 (1.44-2.19) for BI in men. In contrast, adjustment for covariates amplified the estimates to 2.36 (1.52-3.66) for BI in women and to 2.05 (1.73-2.44) for ICH in men. Conclusions: Risk of stroke mortality was highest in the lowest income group, with a gradient for the intermediate groups, in both women and men. The risk of mortality from BI was highest in women with the lowest income and the risk of ICH was highest in men with the lowest income.