Occupational class inequalities in all-cause and cardiovascular mortality in Norwegian men and women: a population-based approach with 45 years follow-up.

Objectives: This study assessed associations of three theoretically different occupational class schemes with all-cause and cardiovascular mortality in Norwegian men and women.
Study Design: Pooled survey and register data from four Norwegian cohort studies.
Methods: We pooled survey data from four general population cohorts (N = 97,469) linked to national mortality registries with follow-up over 45 years. Survival was modelled using accelerated failure time models stratified by sex for three class schemes: The European Socio-Economic Classification (ESeC), The Oslo Register Data Class scheme (ORDC) and The International Socio-Economic Index (ISEI). Main analyses were adjusted for age, birth cohort, and study. Secondary analyses included smoking behaviour as a mediator.
Results: During median 27.6 years of observation, 37,488 participants had died (13,243 from cardiovascular disease). Hazard ratios for male all-cause mortality were lowest in the highest occupational class categories ORDC 2: 0.68 (0.65-0.72), ESeC 1: 0.76 (0.73-0.79) and ISEI 5th quintile: 0.80 (0.77-0.82) compared to working class reference categories. Female mortality risks were lowest for Cultural Lower Middle class ORDC 7: 0.84 (0.72-0.98), Small Employers and Self-employed ESeC4: 0.70 (0.50-0.97) and ISEI 5th quintile: 0.79 (0.70-0.90). Patterns for cardiovascular mortality were similar to all-cause mortality. Including smoking behaviour as a mediator attenuated associations, but overall mortality patterns according to occupational class remained unchanged.
Conclusion: The results underline that mortality inequalities do not simply consist of higher risks in the most disadvantaged groups. The association of occupational class with mortality is found across different categories of occupational class schemes, illustrating their continued relevance for studying social determinants of health.
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