BACKGROUND

Individuals adopt particular health-related practices according to what is structurally possible for them. Given that many health-related practices and obesity are patterned by socioeconomic position (SEP) and strongly linked with mortality, they may represent mechanisms through which SEP becomes biologically embedded and influences mortality risk. This study quantified whether and to what extent health-related practices (current/former smoking, physical inactivity, low fruit and vegetable intake, excess alcohol intake) and obesity mediate associations between SEP and all-cause and cancer mortality in a nationally representative cohort of adults in Canada.

METHODS

This was a prospective, population-based cohort study of adults (≥ 35 years; n = 308,635) who participated in the cross-sectional Canadian Community Health Survey. Data from eight survey cycles (2000/2001-2011) were linked to mortality records in the Canadian Mortality Database (2000-2013). Household income adequacy and educational attainment were used to generate a latent variable representing SEP at baseline. Participants also self-reported smoking, physical activity, fruit and vegetable intake, alcohol intake and BMI at baseline. Generalized Structural Equation Modeling was performed to evaluate pathways linking SEP with all-cause and cancer mortality mediated by health-related practices (current/former smoking, physical inactivity, low fruit and vegetable intake, excess alcohol intake) and obesity in males and females.

RESULTS

Health-related practices and obesity did not collectively mediate associations between lower SEP and all-cause or cancer mortality in males or females. However, current/former smoking mediated associations between lower SEP and all-cause (males: HR 1.06, 95% CI 1.01, 1.12; females: HR 0.97, 95% CI 0.95, 0.99) and cancer mortality (males: HR 1.06, 95% CI 1.01, 1.12; females: HR 0.97, 95% CI 0.95, 0.99) in males and females, and physical inactivity mediated associations between lower SEP and all-cause mortality in females (HR 1.12, 95% CI: 1.03, 1.21). Low fruit and vegetable intake, excess alcohol intake and obesity did not mediate associations between lower SEP and mortality.

CONCLUSIONS

Smoking and physical activity may represent mechanisms through which SEP becomes biologically embedded and shapes the risk of mortality among adults in Canada. However, most of the associations between SEP and mortality remained unexplained; thus, additional studies are needed to understand other pathways of biological embedding.