The Role of Social Stress in Body Composition: Results From the Women’s Health Initiative

Abstract

Introduction: Changes in several body composition systems are responsible for a high burden of chronic conditions among aging adults. Bone loss and obesity are particularly important proximal risk factors of chronic conditions among aging women. There is evidence that psychosocial stress related to socioenvironmental factors is a distal risk factor for both body composition changes and chronic disease outcomes. The overall objective of this dissertation was to establish a temporal association between social stress with body composition factors, fat and bone, to improve understanding of the pathway through which social stress alters chronic disease outcomes among postmenopausal women. Methods: To address the overall objective, this dissertation undertook three studies using data from the Women’s Health Initiative (WHI) health study. The exposure for the studies were three psychosocial constructs related to the social environment: social strain, social functioning, and social support. One study evaluated social stress with time to fracture incidence using data from the WHI main study (N=161,808). The remaining two studies used data from the WHI Bone Mineral Density (BMD) sub-cohort (N=11,020) to evaluate BMD and visceral adipose tissue (VAT) outcomes. Results: High social stress was associated with greater loss of BMD over six years. After adjustment for confounders, each point higher social strain was associated with a 0.082% greater loss of femoral neck BMD, 0.108% loss of total hip BMD, and 0.069% loss of the lumbar spine BMD (P<0.05). In the second study, social stress was associated with greater risk of total and hip fractures. Social functioning had the greatest magnitude of effect with each one SD higher score, representing lower stress, associated with lower risk of total fractures (HR=0.90; 95% CI: 0.89 to 0.91) and hip fractures (HR=0.87; 95% CI: 0.84 to 0.89). In the third study, results from linear mixed models showed that social stress was longitudinally associated with greater VAT area and visceral/subcutaneous adipose tissue ratio. Age and race/ethnicity modified associations between social stress with fractures and VAT outcomes. Conclusion: The findings of this dissertation provide evidence for an association between social stress and detrimental changes in body composition. Women with high social stress were found to have greater longitudinal risk for decreased BMD, fracture incidence, and greater VAT. The results also suggest heterogeneity in the effect of social stress on body composition by race/ethnicity and age. Future research is needed to determine causal effects of social stress in body composition changes.