Physical activity in women may reduce risk for some fractures over time
An analysis of data from the Women's Health Initiative found that total physical activity in postmenopausal women was inversely associated with risk of total and hip fracture but positively associated with risk of knee fracture over 14 years of follow-up.
Higher total physical activity was associated with lower total and hip fracture risk but higher knee fracture risk over time in older ambulatory women, a study found.
Researchers looked at data from 77,206 postmenopausal women in the Women's Health Initiative to examine whether total, mild, moderate to vigorous, and walking physical activity were associated with fracture risk over time. The study's main outcome measures were total and site-specific fracture incidence. Results were published on Oct. 25 by JAMA Network Open.
The mean age of the study participants was 63.4 years, and most (85.6%) were white. During a mean follow-up of 14 years, moderate to vigorous physical activity was associated with wrist or forearm fractures and sedentary behavior was associated with total fractures. Overall, 25,516 women (33.1%) reported a first incident fracture during the follow-up period.
Total physical activity (>17.7 metabolic equivalent hours of exercise per week vs. none) was inversely associated with multivariable-adjusted risk of hip fracture (hazard ratio [HR], 0.82; 95% CI, 0.72 to 0.95; P<0.001 for trend) but was positively associated with knee fracture (HR, 1.26; 95% CI, 1.05 to 1.50; P=0.08 for trend). Inverse associations with hip fracture were also observed for walking (HR, 0.88; 95% CI, 0.78 to 0.98; P=0.01 for trend), mild activity (HR, 0.82; 95% CI, 0.73 to 0.93; P=0.003 for trend), moderate to vigorous activity (HR, 0.88; 95% CI, 0.81 to 0.96; P=0.002 for trend), and yard work (HR, 0.90; 95% CI, 0.82 to 0.99; P=0.04 for trend).
Mild activity was associated with lower risks of clinical vertebral fracture (HR, 0.87; 95% CI, 0.78 to 0.96; P=0.006 for trend) and total fractures (HR, 0.91; 95% CI, 0.87 to 0.94; P<0.001 for trend), while moderate to vigorous activity was positively associated with wrist or forearm fracture (HR, 1.09; 95% CI, 1.03 to 1.15; P=0.004 for trend). After the researchers controlled for covariates and total physical activity, a positive association was seen between sedentary time and total fracture risk (HR for >9.5 h/d vs. <6.5 h/d, 1.04; 95% CI, 1.01 to 1.07; P=0.01 for trend). Some of this risk was mitigated by a higher total level of activity.
An editorial urged caution in interpretation of the results, noting that exercise is a complex intervention and that types of activity and activity levels vary over time. While the study authors acknowledged the limitations of their study, the editorialist questioned whether such acknowledgment was enough. Future studies should routinely address such issues as measurement error and multiplicity adjustment in order to arrive at more robust results, the editorialist concluded.