Association of Interleukin‐6 and Other Biologic Variables with Depression in Older People Living in the Community

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Abstract
The prevalence of depression increases with age, as does the prevalence of higher levels of the cytokine interleukin-6 (IL-6). This analysis was performed to determine the association between increased levels of this cytokine and depression in a population-based sample. Cross-sectional cohort study. Rural and urban counties in North Carolina. Community-dwelling older people. The association between IL-6 and other biologic variables with self-report depression was examined in 1686 persons aged 70 years and older in the third in-person survey wave (1991) of the Duke Established Population for Epidemiologic Studies of the Elderly (EPESE). Bivariate associations were established by the Spearman correlation, adjusted for age. A stepwise linear logistic regression model was used to derive a final model to assess multivariable effects on CES-D scores. Depression was correlated with IL-6 (P = .011), D-Dimer (P = .017), alpha-1-globulin (P = .023), alpha-2-globulin (P = .002), and beta globulin (P = .012). After controlling for age, race, and gender, IL-6 levels remained the only biologic variable significantly associated with depression (P = .035). These data suggest that the inflammatory marker, IL-6, is associated with depression in older people in this cross-sectional study. These results are compatible with the hypothesis of cytokine (IL-6) stimulation in geriatric depression as part of an overall immunoendocrine dysregulation.