Association of interleukin-6 and other biologic variables with depression in older people living in the community

OBJECTIVES: The prevalence of depression increases with age, as does the pr evalence of higher levels of the cytokine interleukin-6 (IL-6). This analys is was performed to determine the association between increased levels of t his cytokine and depression in a population-based sample. DESIGN: Cross-sectional cohort study. SETTING: Rural and urban counties in North Carolina. PARTICIPANTS: Community-dwelling older people. MEASUREMENTS: The association between IL-6 and other biologic variables wit h self-report depression was examined in 1686 persons aged 70 years and old er in the third in-person survey wave (1991) of the Duke Established popula tion for Epidemiologic Studies of the Elderly (EPESE). Bivariate associatio ns were established by the Spearman correlation, adjusted for age. A stepwi se linear logistic regression model was used to derive a final model to ass ess multivariable effects on CES-D scores. RESULTS: Depression was correlated with IL-6 (P = .011), D-Dimer (P = .017) , alpha-1-globulin (P = .023), alpha-2-globulin (P = .002), and beta globul in (P = .012). After controlling for age, race, and gender, IL-6 levels rem ained the only biologic variable significantly associated with depression ( P = .035). CONCLUSION: These data suggest that the inflammatory marker, IL-6, is assoc iated with depression in older people in this cross-sectional study. These results are compatible with the hypothesis of cytokine (IL-6) stimulation i n geriatric depression as part of an overall immunoendocrine dysregulation.