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

Objectives: 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.

Methods: 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.

Results: 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.

Conclusion: 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.