Inflammation, sleep disturbances, and depressed mood among community-dwelling older men

High rates of sleep disturbances occur in depression. Sleep disturbances are linked to heightened inflammation. We sought to determine if sleep disturbances explain a portion of the putative inflammation - depression association among older adults. In late life, age-related immunoregulation changes may modify the inflammation-depression relationship.

Cross-sectional associations of a panel of serum inflammatory markers with probable depression (measured with the Geriatric Depression Scale) were assessed among 2560 community-dwelling older men. We tested whether inflammatory marker - probable depression associations were independent of chronic diseases, as well as objective and subjectively measured sleep disturbances. We also tested whether inflammation-probable depression associations were moderated by age.

Inflammatory markers were not independently associated with higher odds of probable depression. A significant age by C-reactive protein (CRP) interaction (p=0.01) was detected such that the strength of the CRP-probable depression association decreased with age. When stratifying by the median age of 76, elevated odds of probable depression were found for men with CRP levels above the median only among the younger group (OR=2.08, 95% CI 1.18-3.69). In the final adjusted model, independent effects of chronic diseases and subjective sleep disturbances contributed to a total of 37% attenuation of the original OR (adjusted OR=1.68, 95% CI 0.911-3.10, p=.09).

In late-life, associations between inflammatory markers and mood may be explained by both chronic diseases and subjectively reported sleep disturbances. Our findings indicate that the association of CRP with probable depression diminishes in strength with age.