Walking and Leisure-Time Activity and Risk of Hip Fracture in Postmenopausal Women

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Physical activity lowers the risk of hip fracture in older women, but whether simply walking (the commonest activity engaged in by older persons) and other leisure time activities have the same effect is not clear. The authors prospectively analyzed data from the Nurses' Health Study cohort of registered nurses in 11 states. The study population included 61,200 postmenopausal women 40 to 77 years of age, nearly all of whom were white. None had cancer, heart disease, stroke, or osteoporosis at the outset. Participants estimated the time they spent in each of seven activities, each of which was assigned a metabolic equivalent (MET) score, with 1 MET being the energy expended while sitting quietly. Walking was by far the most popular activity, accounting for two thirds of total MET hours per week. The median time spent walking was 1.25 hours per week. There were 415 incident hip fractures during the 12-year follow-up period covering the years 1986-1998. After controlling for age, body mass index (BMI), hormone use, smoking, and dietary intake, the risk of hip fracture fell 6% for each increase of 3 MET hours of activity per week (the equivalent of 1 hour per week of walking at an average pace). BMI also correlated significantly, inversely, and independently with the risk of hip fracture. Women with at least 24 MET hours of activity per week had a 55% lower risk of hip fracture than sedentary women with less than 3 MET hours per week (relative risk, 0.45). Even women whose reduced risk correlated with higher body weight had a further reduction in risk when they were more active. In women not taking postmenopausal hormones, the fracture risk declined linearly with increasing activity, but no such relationship was noted in those taking hormones. Compared with women exercising less than 1 hour a week, those who walked for 4 or more hours but did no other exercise had a 41% lower risk of hip fracture (relative risk, 0.59). The pace of walking was also a significant predictor of risk. Women who reported standing for 55 or more hours per week had a 46% lower risk of hip fracture than those who stood for less than 10 hours, and those walking very briskly had a 65% risk reduction. Through engaging in regular leisure time activities, including walking, postmenopausal women, whether lean or heavy, are able to lower their risk of hip fracture.