Life-course socioeconomic factors are associated with markers of epigenetic aging in a population-based study

Adverse socioeconomic circumstances negatively affect the functioning of biological systems, but the underlying mechanisms remain only partially understood. Here, we explore the associations between life-course socioeconomic factors and four markers of epigenetic aging in a population-based setting. We used data from a population-based study conducted in Switzerland (SKIPOGH) to assess the association between childhood, adulthood, and life-course socioeconomic indicators, and blood-derived markers of epigenetic aging (Levine, DunedinPoAm38, GrimAge epigenetic age acceleration (EAA) and the mortality risk score (MS)). We used mixed regression to explore the associations between socioeconomic indicators and markers of epigenetic aging independently, and counterfactual mediation to investigate the mechanisms underlying the life-course socioeconomic gradient in epigenetic aging. Individuals reporting a low paternal occupation, adverse financial conditions in childhood, a low income, having financial difficulties, or experiencing unfavorable socioeconomic trajectories were epigenetically older than their more advantaged counterparts. Specifically, this corresponded to an average increase of 1.0-1.5 years for Levine epigenetic age when compared to chronological age, 1.1-1.5 additional years for GrimAge, 5%-8% higher DunedinPoAm38 EAA, and 2%-5% higher MS score. By exploring the life-course mechanisms underlying the socioeconomic gradient in epigenetic aging, we found that both childhood and adulthood socioeconomic factors contributed to epigenetic aging, and that detrimental lifestyle factors mediated the relation between socioeconomic circumstances in adulthood and EAA. Our study provides novel empirical evidence for a sensitive-period life-course model, whereby adverse socioeconomic circumstances in childhood and adulthood negatively affected epigenetic aging. Counterfactual mediation analyses further showed that the effect of socioeconomic factors in adulthood operated through detrimental lifestyle factors, whereas associations involving early-life socioeconomic factors were less clear.