PHYSICAL-ACTIVITY AND OSTEOPOROTIC FRACTURE RISK IN OLDER WOMEN

Background: Physical activity has been related to enhanced bone mass a nd improved physical functioning and thus may reduce the risk for oste oporotic fracture. Objective: To determine whether higher levels of ph ysical activity are related to lower incidence of hip, wrist, and vert ebral fractures. Design: Prospective cohort study. Setting: Four clini cal centers in Baltimore, Maryland; Portland, Oregon; Minneapolis, Min nesota; and the Monongahela Valley, Pennsylvania. Participants: 9704 n onblack women 65 years of age or older. Measurements: Physical activit y was assessed by questionnaire at baseline. Hip and wrist fractures w ere followed for an average of 7.6 years. The incidence of vertebral f racture was determined morphometrically by using radiography at baseli ne and an average of 3.7 years later. Results: Higher levels of leisur e time, sport activity, and household chores and fewer hours of sittin g daily were associated with a significantly reduced relative risk for hip fracture after adjustment for age, dietary factors, falls at base line, and functional and health status. Very active women (fourth and fifth quintiles) had a statistically significant 36% reduction in hip fractures (relative risk, 0.64 [95% CI, 0.45 to 0.89]) compared with t he least active women (lowest quintile). The intensity of physical act ivity was also related to fracture risk: Moderately to vigorously acti ve women had statistically significant reductions of 42% and 33% in ri sk for hip and vertebral fractures, respectively, compared with inacti ve women. Total physical activity, hours of household chores per day, and hours of sitting per day were not significantly associated with wr ist or vertebral fractures. Conclusions: Among older community-dwellin g women, physical activity is associated with a reduced risk for hip f racture but not wrist or vertebral fracture.