Beyond smoking: Education, marital status and mortality in 513,552 Norwegians

Background: Smoking is closely linked to socioeconomic status and risk of death. We examined the extent to which educational disparities in mortality can be explained by smoking. Methods: We analysed data from 513,552 men and women aged 25–69 years, excluding individuals with a history of cardiovascular disease, diabetes or cancer. The educational level was lower (less than 10 years), upper (10–12 years) and higher (13 or more years). We employed the direct method to estimate age-adjusted mortality rates and used the Cox proportional hazards model to calculate hazard ratios, using a higher educational level as the reference level. We ran models among non-smokers with interaction terms, educational level and another variable. Based on Akaike information criterion, we performed stratified analyses by marital status among non-smokers. Results: The hazard ratio for lower educational level in men was 1.38 (1.31–1.45) in non-smokers and 1.57 (1.49–1.66) in smokers. The figures for women were almost identical. Among non-smoking men, the hazard ratio for lower educational level was 1.28 (1.21–1.35) for the ever married and 2.20 (1.93–2.52) for the unmarried men. In women the figures were the same. For non-smoking men and women combined, the population attributable risk ascribed to upper or lower educational level was 17% for the ever married and 35% for the unmarried. Conclusions: An educational gradient in mortality persists in the absence of smoking and is more pronounced among the unmarried. Marital status appears to modify the relationship between education and mortality, underscoring the need to consider social and relational factors in health inequality research.