Socio-economic inequalities in cause-specific mortality: a 16-year follow-up study

To examine socio-economic inequalities in cause-specific mortality by examining the independent effects of education, occupation and income in a population-based study of working-age Canadian adults.

This is a secondary analysis of data from the 1991-2006 Canadian Census mortality and cancer follow-up study (n=2.7 million persons). For this analysis, the cohort was restricted to 2.3 million persons aged 25 to 64 at cohort inception, of whom 164,332 died during the follow-up period. Hazard ratios were calculated by educational attainment (4 levels), occupational skill (6 categories) and income adequacy (5 quintiles) for all-cause mortality and major causes of death. Models were run separately for men and women, controlled for multiple variables simultaneously, and some were stratified by 10-year age cohorts.

The magnitude of socio-economic inequalities in mortality differed by indicator of socio-economic position (education, occupation, or income), age group, sex, and cause of death. Compared to age-adjusted models, hazard ratios were attenuated but remained significant in models that adjusted for both age and all three indicators of socio-economic position simultaneously. Socio-economic inequalities in mortality were evident for most of the major causes of death examined.

This study demonstrates that education, occupation and income were each independently associated with mortality and were not simply proxies for each other. When evaluating socio-economic inequalities in mortality, it is important to use different indicators of socio-economic position to provide a more complete picture.