Perceived Stress, Insulin Resistance, and the Effects of Physical Activity

摘要

Perceived stress has been associated with the development of insulin resistance and hyperglycemia in cross-sectional studies of midlife adults, but few studies have investigated the effects of perceived stress longitudinally, particularly among midlife women. The primary goal of this dissertation was to assess how inter-individual variability in perceived stress, measured longitudinally over time, affected insulin resistance, and to evaluate whether physical activity modified the risk of insulin resistance associated with perceived stress.;Participants were premenopausal women, ages 42--52 years, recruited for the Study of Women's Health Across the Nation (SWAN). Baseline interviews occurred from 1996--1997, and women were followed approximately annually over 13 study visits. Sociodemographic information included site of recruitment, self-reported race / ethnicity, educational attainment, and baseline financial hardship. Health measures including height and weight, waist circumference, fasting insulin and glucose levels, menopausal status, perceived stress, and physical activity participation were collected at most study visits. Longitudinal mixed-effects models assessed the effects of sociodemographic variables and changing menopausal status on perceived stress and physical activity over time, and the effects of longitudinal perceived stress and total physical activity, adjusted for other health measures, on insulin resistance.;Mean levels of perceived stress decreased for most women as they transitioned across the midlife, but increased over time for women living in Newark, New Jersey. Women with lower educational attainment or higher financial hardship consistently reported higher levels of perceived stress, although this difference diminished with time. After adjustment for other sociodemographic variables, race / ethnicity was a significant predictor of increased perceived stress only for Japanese women. Menopausal status was not associated with perceived stress after adjustment for age and sociodemographic factors.;SWAN women participated in a moderate amount of total physical activity -- including household and childcare, non-sport leisure, and sports and exercise activity---consistently across the midlife. Small longitudinal variations were observed within individual physical activity indices: average household and childcare activities dipped for women in their fifties, but increased in their sixties; non-sport leisure activity slowly declined; while sports and exercise participation increased over the midlife. Physical activity participation was significantly influenced by socioeconomic status, but also by geographic location.;Increased longitudinal perceived stress and higher baseline perceived stress, adjusted for age, race / ethnicity, and menopausal status, were associated with increased insulin resistance, although the results were not statistically significant after adjustment for total physical activity and waist circumference. Factors significantly associated with insulin resistance after adjustment for age and waist circumference included race / ethnicity, changing menopausal status, and total physical activity.;This dissertation significantly expands our understanding of the factors affecting risk of insulin resistance as women traverse the midlife. Strong associations for increasing insulin resistance---independent of adiposity---were observed for race / ethnicity, physical activity, and menopausal status. However, reported perceived stress was higher and physical activity was lower among racial / ethnic minorities in SWAN, compounding risk and contributing to a disparity that has existed despite decades of research. Efforts to increase regular physical activity must continue, particularly efforts that are culturally or socioeconomically sensitive, to ensure an impact on the health of these individuals at higher risk, and prevent entry into the healthcare system. Finally, without substantial changes in adiposity or physical activity trends, women may need to be routinely screened for diabetes onset during the menopause.