Physical activity, hormone replacement therapy, and insulin resistant coronary artery disease risk factors in postmenopausal women

Graduation date: 2002Low physical activity levels and high serum C-reactive protein (CRP) levels are risk\ud factors for coronary artery disease (CAD) in both men and women. However,\ud postmenopausal women who take hormone replacement therapy (HRT) may have\ud increased risk of CAD because of HRT-related increases in serum CRP. There are two\ud manuscripts in this dissertation. The purpose of the first manuscript was to determine\ud whether higher physical activity energy expenditure was associated with lower serum\ud CRP, independent of oral HRT status and body fatness, in 133 postmenopausal women.\ud Higher physical activity energy expenditures were significantly associated with lower\ud serum CRP levels (r=-0.21, p=0.0l9), independent of oral HRT use, age, smoking\ud behavior, alcohol consumption, aspirin use, and statin use. However, in the complete\ud multivariate model, which included body fat, the association between higher physical\ud activity and lower serum CRP levels was abolished. The purpose of the second study\ud was to quantify the biological variability of insulin resistant CAD risk factors in a sample\ud of 8 postmenopausal women. Risk factor outcomes, including serum total cholesterol,\ud serum triglycerides (TG), serum high-density lipoprotein cholesterol (HDL-C), serum\ud glucose, plasma insulin, serum CRP, waist and hip circumferences, abdominal sagittal diameter, body fat, systolic (SBP) and diastolic blood pressure, and self-reported physical\ud activity energy expenditure, were measured on two occasions, 7-12 days apart. High\ud absolute biological variability values (by standard error of measurement) were observed\ud for serum TG (32.0 mg/dl), serum CRP (5.6 mg/l), SBP (4.0 mmHg), and physical\ud activity (9.4 kcal/kg/week). High relative biological variability (by within-subjects\ud coefficient of variation ≥27.3%) was also observed for serum TG, serum CRP, and\ud physical activity. Bland-Altman plots identified individual outliers for serum TG, serum\ud CRP, plasma insulin, and SBP. Together, the results suggest that the correlations\ud between lower levels of serum CRP and higher levels of physical activity, though\ud significant, may have been attenuated by the high biological variability of both serum\ud CRP and physical activity. Thus, the importance of higher levels of physical activity, in\ud decreasing serum CRP and the concomitant risk of heart disease, may be underestimated\ud in the absence of serial measurement of serum CRP and physical activity