The role of sex and stress hormones in the earliest stages of AL

This research is an original investigation into how sleep mediates the relationships between life stressors, healthy habits, resilience and allostatic load (AL) in mid-life adults. Using data from 620 participants with a mean age of 51.3 years, the team applied structural equation modeling to test two mediation models that examined how traumatic and psychosocial stressors and engagement in healthy behaviors—including physical activity, cognitive activity, and dietary patterns—relate to a composite index of physiological wear-and-tear represented by AL.

AL is conceptualized here as an integrative biomarker index composed of inflammatory, metabolic, and cardiovascular measures, and is framed as a systemic indicator associated with risk for multiple adverse health outcomes, including cognitive decline and Alzheimer’s disease. The investigators constructed Model 1 to evaluate direct and indirect effects of life stressors, lifestyle behaviours (sports, cognitive activities, and diet), and resilience on AL. Model 2 extended this framework by explicitly incorporating self-reported sleep quality as a mediator between resilience, perceived influence of stressors, and AL. Across models, consistent direct effects of sports and diet on AL were observed, alongside effects of sports on resilience. Critically, the modulation of AL by both traumatic and psychosocial stressors emerged only when sleep quality was included in the mediation analysis (Model 2). In that model, the perceived influence of stressors exerted indirect effects on AL via sleep quality, indicating that how individuals perceive the impact of stressors affects their sleep, which in turn influences physiological dysregulation. Moreover, the protective effect of sports habits on AL via enhanced resilience was found to be further mediated by sleep, revealing a chain in which physical activity promotes resilience, which supports better sleep, and thereby contributes to lower AL.

Importantly, the study revealed equivalent but opposite influences of perceived stress and resilience on sleep quality: perceived stressors tended to worsen sleep while resilience promoted better sleep; the balance between these opposing forces was identified as a critical determinant of resulting AL. The authors conclude that sleep plays a pivotal, integrative role in balancing the harmful and protective pathways linking life stressors and healthy habits to systemic physiological burden. The implication is that interventions targeting sleep quality—in conjunction with promoting physical activity, dietary health, and resilience—may be particularly influential in attenuating allostatic load in mid-life, thereby potentially lowering risk trajectories associated with chronic disease and cognitive decline. This work highlights the necessity of considering sleep as a central mediator in psychosocial and lifestyle models of physiological aging and underscores the complex interplay between subjective stress appraisal, adaptive coping (resilience), health behaviours, and biological outcomes in mid-life adults.