Habitual Physical Activity and Bone Mineral Density in Postmenopausal Women in England

Background: Reduced levels of physical activity have been found to be associated with an increased risk of osteoporotic fracture in a number of epidemiological studies, and intervention studies have shown beneficial effects of exercise regimes on bone mineral density. It is not yet established, however, which specific forms of customary physical activity are most strongly associated with bone mineral density in postmenopausal women.

Methods: A cross-sectional study was conducted in 580 postmenopausal women, aged 45-61 years, resident in Nottingham, England. The participants completed a detailed interviewer-administered activity questionnaire. Physical activity was assessed as total hours of participation per week in activities including housework, walking, gardening and sports. Stair-climbing and self-reported walking pace were also reported. Bone mineral density measurements were made using dual energy x-ray absorptiometry, measurements at five sites were used in analysis.

Results: The strongest associations between the activity measures and bone mineral density were for stair-climbing and walking pace, which both gave statistically significant positive associations at the trochanter hip site and the whole body. In women reporting a fairly brisk or fast walking pace, bone mineral density at the proximal femur was also significantly and positively associated with the frequency of walking at least a mile. There were no significant associations with aggregate measures of total customary physical activity.

Conclusions: This study has identified two forms of physical activity, namely stair-climbing and brisk walking which are associated with increased bone mineral density at the hip and whole body in postmenopausal women. Both are feasible forms of activity for promoting to middle-aged women.