Lifetime socio-economic position and depression: an analysis of the influence of cognitive function, behaviour and inflammatory markers

Background: Little is known about the influence of lifetime socio-economic position (SEP) on adult depression. We examined the association of SEP during the life course with depressive mood in late midlife and explored whether cognitive function at age 20, health-related behaviour and inflammatory biomarkers explained any associations. Methods: A cohort of 2482 Danish men born in 1953 with information from birth, and conscript board examinations was followed-up with assessment of depressive mood and blood sampling in 2010. Simple and multiple linear regression were used to investigate associations among variables. Results: Social circumstances during the life course were associated with depressive mood. Further, low lifetime SEP was associated with lower cognitive score, smoking, alcohol use, high body mass index (BMI) and increased level of high sensitive ProReactive Protein and Interleukin-6. These covariables were also associated with depressive mood and when they were included into the regression model together with life time SEP, the beta-estimates for the latter attenuated, when smoking, alcohol and BMI were entered, while the inclusion of cognitive function and the inflammatory biomarkers had limited effect on the relation between lifetime SEP and depressive mood. Conclusions: Lifetime SEP was associated with depressive mood and health-related behaviour explained a part of the relation.