| Background. Properties of body composition and body fat distribution associated with aging, such as sarcopenia and abdominal fat accumulation, may be indicated by smaller hip circumference(HC). This dissertation investigated associations of hip circumference and type 2 diabetes, coronary heart disease, hip fracture and functional limitations independent of other anthropometrics.;Methods. Three distinct research projects had the common goals of describing associations of HC with chronic diseases (1) type 2 diabetes and coronary heart disease (CHD) (2) hip fractures and (3) physical functioning. The first project uses data from the Atherosclerosis Risk in Communities study. The second and third projects use data from the Iowa Women's Health Study. Proportional hazards regression was used to characterize the prospective associations of hip circumference with type 2 diabetes, CHD and hip fracture. Using growth curve analysis, trajectories of physical functioning were described and regressed on anthropometric predictors.;Results. Results for the three projects were as follows: (1) In a cohort of 10,767 Black and White men and women aged 45-64 years at baseline, compared to the lowest quintile, successive quintiles of HC were associated with a reduced hazard of incident diabetes after controlling for waist circumference (WC), BMI and confounding variables (HR =1.00, 0.79, 0.60, 0.44, 0.41). Compared to the lowest quintile, successive quintiles of HC were associated with reduced hazard of CHD during follow-up after controlling for WC, BMI and confounding variables (HRs=1.00, 0.94, 0.76, 0.56, 0.52). (2) Compared to the lowest quintile, successive quintiles of hip circumference were associated with a reduced hazard of hip fracture over (HRs=1.00, 0.78, 0.74, 0.76, 0.69) in a cohort of 30,652 postmenopausal women aged 55-70 years at baseline. After controlling for BMI, the association with HC was attenuated to the null while the association with successive quintiles of BMI remained significant and inverse (1.00, 0.55, 0.45, 0.40, 0.35). (3) Declines in physical functioning over 15 years were best described by a negative slope with a quadratic component across three age groups in a cohort of 26,294 postmenopausal women who were free of disease at baseline. After controlling for BMI, compared to the lowest quintile, successive quintiles of HC were estimated to have poorer physical functioning over time. Declines in functioning were greatest in the oldest age group(65-70 at baseline).;Conclusion. These results suggest that while HC is inversely associated with type 2 diabetes and CHD after controlling for WC and BMI, in terms of fracture risk, BMI may be more important. Larger HC predicted greater declines in self-reported functioning after controlling for BMI. These results suggest that HC indicates different qualities of body composition in different disease pathways. Future research should characterize changes in body composition at the femoral-gluteal region, particularly in aging populations. |
