Exercise Builds Strong Bones

(excerpted from the Los Angeles Times, 11/25/02)


A study published on November 13, 2002 in the Journal of the American Medical Assn. found that post-menopausal women who walked four or more hours a week had a 41% lower risk of hip fractures compared with those who did little or no exercise. The study found that among women who exercised the most, eight or more hours a week, the reduction in the risk of a hip fracture was essentially the same as taking hormone replacement therapy.

In fact, any exercise -- even standing, as opposed to sitting -- reduced the risk of hip fracture, said the study's lead author, Diane Feskanich, an assistant professor at Brigham and Women's Hospital in Boston.

The study, part of the ongoing Nurses Health Study, included 61,200 post-menopausal women ages 40 to 77 who were followed from 1986 to 1998. Those women who stood 55 hours a week or more had a 46% lower risk of hip fracture compared with couch potatoes.

"One could say that doing anything rather than sitting and watching TV will help," Feskanich said. "The point is, you get more benefit the more you do."

Standing 55 hours or more a week sounds a little tough, but walking or some other form of exercise isn't. And it's good for so much else: It reduces the risk of heart disease and stroke by lowering blood pressure and raising HDL, the so-called "good cholesterol." It helps with weight control and reduces the risk of Type 2 diabetes. It helps with balance and flexibility. It helps reduce the pain from joint problems. It can improve the quality of sleep. It often reduces the symptoms of depression, and a recent study showed it helps keep older people mentally sharper.

There's no down side to moving your body "unless you overdo it, and we're not talking about that," Feskanich said.

JAMA Abstract:

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

Diane Feskanich, ScD; Walter Willett, MD, DrPH; Graham Colditz, MD, DrPH

Context: Physical activity can reduce the risk of hip fractures in older women, although the required type and duration of activity have not been determined. Walking is the most common activity among older adults, and evidence suggests that it can increase femoral bone density and reduce fracture risk.

Objective: To assess the relationship of walking, leisure-time activity, and risk of hip fracture among postmenopausal women.

Design, Setting, and Participants: Prospective analysis begun in 1986 with 12 years of follow-up in the Nurses' Health Study cohort of registered nurses within 11 US states. A total of 61 200 postmenopausal women (aged 40-77 years and 98% white) without diagnosis of cancer, heart disease, stroke, or osteoporosis at baseline.

Main Outcome Measures: Incident hip fracture resulting from low or moderate trauma, analyzed by intensity and duration of leisure-time activity and by time spent walking, sitting, and standing, measured at baseline and updated throughout follow-up.

Results: From 1986 to 1998, 415 incident hip fracture cases were identified. After controlling for age, body mass index, use of postmenopausal hormones, smoking, and dietary intakes in proportional hazards models, risk of hip fracture was lowered by 6% (95% confidence interval [CI], 4%-9%; P<.001) for each increase of 3 metabolic equivalent (MET)?hours per week of activity (equivalent to 1 h/wk of walking at an average pace). Active women with at least 24 MET-h/wk had a 55% lower risk of hip fracture (relative risk [RR], 0.45; 95% CI, 0.32-0.63) compared with sedentary women with less than 3 MET-h/wk. Even women with a lower risk of hip fracture due to higher body weight experienced a further reduction in risk with higher levels of activity. Risk of hip fracture decreased linearly with increasing level of activity among women not taking postmenopausal hormones (P<.001), but not among women taking hormones (P = .24). Among women who did no other exercise, walking for at least 4 h/wk was associated with a 41% lower risk of hip fracture (RR, 0.59; 95% CI, 0.37-0.94) compared with less than 1 h/wk. More time spent standing was also independently associated with lower risks.

Conclusion: Moderate levels of activity, including walking, are associated with substantially lower risk of hip fracture in postmenopausal women.

JAMA. 2002;288:2300-2306