Based on a mean follow-up period of 14.0 years, the researchers found that total physical activity was inversely associated with the multivariable-adjusted risk of hip fracture (> 17.7 MET h/wk vs none: HR, 0.82; 95% CI, 0.72-0.95; P for trend < .001). Inverse associations with hip fracture were also observed for walking (> 7.5 MET hr/wk vs none; HR, 0.88; 95% CI, 0.78-0.98; P for trend = .01), mild activity (HR, 0.82; 95% CI, 0.73-0.93; P for trend = .003), moderate to vigorous activity (HR, 0.88; 95% CI, 0.81-0.96); P for trend = .002) and yard work (HR, 0.90; 95% CI, 0.82-0.99; P for trend = .04).
Mild activity was associated with lower risks of clinical vertebral fracture (HR, 0.87; 95% CI, 0.78-0.96; P for trend = .006) and total fractures (HR, 0.91; 95% CI, 0.87-0.94; P for trend < 0.01). Moderate to vigorous activity was positively associated with wrist or forearm fracture (HR, 1.09; 95% CI, 1.03-1.15; P for trend = .004). After controlling for covariates such as age, history of fracture after age 55 and bone drug use, and total physical activity, sedentary time was positively associated with total fracture risk (> 9.5 h/d vs < 6.5 h/d: HR, 1.04; 95% CI, 1.01-1.07; P for trend = .01). When analyzed jointly, higher total activity mitigated some of the total fracture risk associated with sedentary behavior.
Noting that there is the most comprehensive evaluation to date of physical activity and fracture incidence in older women, the authors concluded that “current results suggest that lower-intensity activities, including walking and nonrecreational activities, could have benefit on fracture risk at older ages.” They believe that if their results are confirmed, light physical activity should be recommended to postmenopausal women to prevent fracture, particular those who cannot safely undertake more intense activity.