How social isolation accelerates biological aging: Exploring underlying behavioral and psychological mechanisms.

RATIONALE: Social isolation can have lasting effects on physiological aging and overall health in older adults. However, few studies have examined the behavioral and psychological mechanisms that mediate the relationship between social isolation and accelerated biological aging.

OBJECTIVE: This study investigates how social isolation contributes to accelerated biological aging over time, focusing on potential behavioral and psychological mechanisms.

METHODS: Data were drawn from the Health and Retirement Study (HRS), involving 4036 U.S. older adults followed from 2006 to 2016. Accelerated biological aging at T3 (2016) was measured using an expanded phenotypic age derived from 22 clinical biomarkers. Social isolation was assessed at T1 (2006/2008), and behavioral (smoking, drinking, physical activity, poor sleep quality) and psychological (depressive symptoms) factors were measured at T2 (2010/2012). Formal mediation analyses estimated indirect effects linking social isolation to accelerated aging.

RESULTS: Social isolation was longitudinally associated with accelerated biological aging after adjusting for sociodemographic, health, and psychosocial confounders. Among behavioral pathways, physical activity (20.3 %), smoking (8.5 %) and poor sleep quality (7.1 %) each accounted for a meaningful portion of the total effect. Depressive symptoms explained about 7.7 % of the association, whereas drinking did not demonstrate a significant mediating effect.

CONCLUSION: These findings highlight the need to address both social and behavioral factors in promoting healthy aging. By exploring how social isolation "gets under the skin," this study adds to growing evidence that social relationships are key determinant of aging outcomes and should be prioritized in policies aimed at reducing social and health disparities among older adults.