Socio-economic disadvantage and body mass over the life course in women and men: results from the Northern Swedish Cohort

Background: Obesity and body mass in adulthood relate both to current and to childhood socio-economic status, particularly in women, but the underlying life course processes are not known. This study aims at examining whether the life course socio-economic status-body mass association in women and men is explained by the cumulative risk or adolescent sensitive period models whether associations are similar at different life course stages; and whether health behaviours explain the associations. Methods: A total of 476 women and 517 men participated in this 27-year prospective cohort study (participation rate 93%). Body mass index was assessed at the age of 16 and 43 years and self-reported at the age of 21 and 30 years. Information on socio-economic status by own or parental (age 16 years) occupation, smoking, snuff, alcohol, physical activity and diet was collected at each age. Results: In women, cumulative socio-economic status and socio-economic status in adolescence were related to body mass index at the age of 16, 21, 30 and 43 years and to the 27-year change in body mass, independently of health behaviours and for adolescent socio-economic status also of later socio-economic attainment. Associations were generally stronger for body mass at older age. In men, associations were mostly non-significant, although health behaviours contributed strongly to body mass. Conclusions: In women, both the sensitive period (in adolescence) and cumulative risk models explain the socio-economic-body mass link. Efforts to reduce the social inequality in body mass in women should be directed at the early life course, but focusing on unhealthy behaviours might not be a sufficient approach.