Allostatic Load, Social Participation, and Healthy Ageing: Longitudinal Evidence on the Impact of Chronic Stress.

Background/Objectives: The study aimed to examine the impact of allostatic load on healthy ageing over a decade and whether social participation attenuates this relationship among older American adults. Methods: Data were extracted from three waves (wave 8, wave 10, wave 13) of the Health and Retirement Study, a longitudinal survey of American adults. The analysis included allostatic load, socioeconomic (education) and demographic (gender, age, ethnicity, and marital status) factors at baseline, social participation in wave 10, and healthy ageing in wave 10 and wave 13. A latent variable was created for allostatic load that included waist circumference, C-reactive protein, glycated hemoglobin, and blood pressure. Healthy ageing was defined as an aggregate measure including freedom from disability, freedom from cognitive impairment, and high physical functioning. Social participation was a dichotomous variable that included individuals' work status, perceived neighbourhood safety, and partaking in volunteer work. Structural equation modelling was used to examine the direct and indirect relationships between these factors and healthy ageing. Results: A total of 14,537 participants with complete data in all waves were included in the analysis. The mean age at baseline was 68.7 years. Results showed a significant association between higher allostatic load and lower healthy ageing (estimate = -0.12, 95% CI: -0.14, -0.11). Allostatic load was negatively associated with social participation (estimate = -0.32, 95% CI: -0.34, -0.30). Social participation showed a positive significant association with healthy ageing, indicating partial buffering that accounted for 12% of the total effect. Higher educational attainment was associated with better healthy-ageing outcomes, whereas non-Black ethnicity was linked to poorer healthy ageing. Conclusions: Elevated allostatic load was associated with poorer ageing outcomes, with social participation partially attenuating the relationship. Higher education predicted more favourable trajectories, while ethnic differences suggested resilience among older Black adults. These results indicate that both physiological and social factors contribute to variations in healthy ageing.