Lifestyle Factors and Bone Mineral Density: The Postmenopausal Estrogen/Progestins Intervention Study

Abstract

The objective of this study was to examine the associations between bone mineral density (BMD) of the spine and hip and several lifestyle factors. The study design used was cross-sectional analysis of baseline data from a clinical trial, using women who participated in the Postmenopausal Estrogen/Progestins Intervention Trial. The main outcome measures were BMD of the lumbar spine (L2-L4), total hip, and femoral neck measured by dual energy x-ray absorptiometry (DEXA). The mean age of the 875 women was 56.1 years. In a multivariate model that included age, body mass index (BMI), years of former estrogen use, and all lifestyle factors under study, leisure time physical activity (LTPA), dietary calcium, and alcohol intake were statistically significantly associated with higher BMD at one or more bone sites. Of the lifestyle factors tested, LTPA had the greatest effect on BMD, and a dose-response effect of LTPA was evident. Mild and moderate activity levels were associated with intermediate levels of benefit. Supplemental calcium intake was inversely associated with BMD at the total hip and femoral neck. No significant association was found between cigarette use, total calcium (diet plus supplement) intake, home or occupational physical activity, or NSAID use and BMD at any site. Higher dietary calcium did not enhance nor did NSAID use reduce the beneficial effect of leisure activity on BMD. Among healthy postmenopausal women, higher levels of LTPA, dietary calcium, and alcohol intake (within a moderate range) were associated with higher BMD. Although causation cannot be assured in a cross-sectional analysis, the findings are consistent with prior reports. A dose-response gradient is also seen with some exposures, supporting causality.