Occupational social class, educational level, smoking and body mass index, and cause-specific mortality in men and women: a prospective study in the European Prospective Investigation of Cancer and Nutrition in Norfolk (EPIC-Norfolk) cohort.

OBJECTIVES: To investigate the independent associations between occupational and educational based measures of socioeconomic status (SES) and cause-specific mortality, and the extent to which potentially modifiable risk factors smoking and body mass index (BMI) explain such relationships. DESIGN, SETTING AND PARTICIPANTS: Prospective population study of 22,486 men and women aged 39-79 years living in the general community in Norfolk, United Kingdom, recruited using general practice age-sex registers in 1993-1997 and followed up for total mortality using death certification to 2006. MAIN
RESULTS: In men a strong inverse relationship was found between social class and all cause, cardiovascular and cancer mortality, with relative risk of social class V compared to I of 2.21 for all cause mortality (95% CI 1.54-3.17, P < 0.001). This was attenuated but not abolished after adjusting for modifiable risk factors, smoking and BMI, with relative risk of social class V compared to I for all cause mortality of 1.92 (95% CI 1.34-2.77, P < 0.001). A similar, but smaller effect was seen in women. Educational status was not associated with mortality independently of social class.
CONCLUSIONS: Social class and education are not necessarily interchangeable measures of SES. Some but not all of the socioeconomic differential in mortality can be explained by potentially modifiable risk factors smoking and BMI. Further understanding of the mechanisms underlying the association of each socioeconomic indicator with specific health outcomes is needed if we are to reduce inequalities in health.