Association between epigenetic age acceleration and depressive symptoms in a prospective cohort study of urban-dwelling adults

Objective: This study tests associations of DNA methylation-based (DNAm) measures of epigenetic age acceleration (EAA) with cross-sectional and longitudinal depressive symptoms in an urban sample of middle-aged adults. Methods: White and African-American adult participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span study for whom DNA samples were analyzed (baseline age: 30-65 years) we included. We estimated three DNAm based EAA measures: (1) universal epigenetic age acceleration (AgeAccel); (2) intrinsic epigenetic age acceleration (IEAA); and (3) extrinsic epigenetic age acceleration (EEAA). Depressive symptoms were assessed using the 20-item Center for Epidemiological Studies-Depression scale total and sub-domain scores at baseline (2004-2009) and follow-up visits (2009-2013). Linear mixed-effects regression models were conducted, adjusting potentially confounding covariates, selection bias and multiple testing (N = 329 participants, similar to 52% men, k = 1.9 observations/participant, mean follow-up time similar to 4.7 years). Results: None of the epigenetic age acceleration measures were associated with total depressive symptom scores at baseline or over time. IEAA - a measure of cellular epigenetic age acceleration irrespective of white blood cell composition - was cross-sectionally associated with decrement in "positive affect" in the total population (gamma(011) +/- SE = -0.090 +/- 0.030, P = 0.003, Cohen's D: -0.16) and among Whites (gamma(011)+/- SE = -0.135 +/- 0.048, P = 0.005, Cohen's D: - 0.23), after correction for multiple testing. Baseline "positive affect" was similarly associated with AgeAccel. Limitations: Limitations included small sample size, weak-moderate effects and measurement error. Conclusions: IEAA and AgeAccel, two measures of EAA using Horvath algorithm, were linked to a reduced "positive affect", overall and among Whites. Future studies are needed to replicate our findings and test bidirectional relationships.