The longitudinal association between inflammation and incident depressive symptoms in men: The effects of hs-CRP are independent of abdominal obesity and metabolic disturbances

Background: This cohort study evaluates whether the association between low-grade inflammation and incident depressive symptoms is independent of abdominal obesity and metabolic disturbances. Methods: A cohort of 1167 non-depressed men aged 35 to 80 years were followed up over 5 years to assess incident depressive symptoms measured by the Centre for Epidemiology Scale-Depression or Beck Depression Inventory-I. Venous tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and high sensitivity C-reactive protein (hsCRP) were quantified at baseline and 5 years. Logistic regression determined whether hsCRP, IL-6 and TNF-α were associated with incident depressive symptoms independent of abdominal obesity and metabolic factors. Ancillary analysis utilizing depression z scores stratified participants by waist circumference ≥ 102 cm and ≥ 2 metabolic disturbances. Results: Incident depressive symptoms occurred in 95 men at 5 years (8.14% of total). Clinically relevant depressive symptoms were associated with baseline hsCRP (adjusted OR = 1.04; 95% CI 1.00-1.07, p = .03) and annualized δhsCRP (adjusted OR = 1.04; 95% CI 1.01-1.08, p = .02). Ancillary analysis showed that the association between annualized δhsCRP and depression z score was only significant in men with waist circumference < 102 cm (β = .19, p < .001) and ≤ 1 metabolic disturbance (β = .18, p < .001). None of the measured cytokines were significantly associated with depression. Conclusions: hsCRP and annualized δhsCRP were positively associated with depressive symptoms in a cohort of men. Further investigation into the role of abdominal obesity and metabolic disturbances in the inflammation-depression hypothesis is warranted.