Lighter-intensity exercise lowers fracture risk in older women: JAMA

USA: Regular exercise, including lighter-intensity activities and less sedentary time, lowers the risk of fracture in older women, finds a recently published study in the JAMA journal.

According to the study, in older ambulatory women, higher total physical activity lowered the risk of total and hip fracture, whereas increased the risk for knee fracture. Mild activity and walking were however associated with a lower risk of hip fracture.

"Fracture has been associated with low bone mineral density (BMD), the propensity to fall, and declines in muscle strength, balance, mobility, and physical functioning," write the authors.

Physical activity is inversely associated with hip fracture risk in older women. However, the association of physical activity with a fracture at other sites and the role of sedentary behaviour remain unclear. Michael J. LaMonte, University at Buffalo, The State University of New York, Buffalo, and colleagues assessed the associations of physical activity and sedentary behaviour with fracture incidence among postmenopausal women in the Women’s Health Initiative (WHI) prospective cohort study -- a prospective cohort study among postmenopausal women with ongoing assessment of fractures.

The WHI study enrolled 77 206 postmenopausal women aged 50 to 79 years between October 1993 and December 1998 at 40 US clinical centres. Participants were observed for outcomes through September 2015, with data analysis conducted from June 2017 to August 2019. During a mean (SD) follow-up period of 14.0 (5.2) years among 77 206 women, 25 516 (33.1%) reported a first incident fracture.

Key findings of the study include:

• Total physical activity was inversely associated with the multivariable-adjusted risk of hip fracture (>17.7 metabolic equivalents [MET] h/wk vs none).


• Inverse associations with hip fracture were also observed for walking (>7.5 MET h/wk vs none), mild activity, moderate to vigorous activity, and yard work.


• Total activity was positively associated with knee fracture (>17.7 MET h/wk vs none: HR, 1.26).


• Mild activity was associated with lower risks of clinical vertebral fracture (HR, 0.87) and total fractures (HR, 0.91).


• Moderate to vigorous activity was positively associated with wrist or forearm fracture (HR, 1.09).


• After controlling for covariates 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).


• When analyzed jointly, higher total activity mitigated some of the total fracture risk associated with sedentary behaviour.


• Analysis of time-varying exposures resulted in somewhat stronger associations for total physical activity, whereas those for the sedentary time were materially unchanged.

"In older ambulatory women, higher total physical activity was associated with lower total and hip fracture risk but higher knee fracture risk. Mild activity and walking were associated with lower hip fracture risk, a finding with important public health implications because these activities are common in older adults. The positive association between sedentary time and total fracture risk requires further investigation," concluded the authors.

More Information: "Association of Physical Activity and Fracture Risk Among Postmenopausal Women" published in the JAMA journal.

DOI: 10.1001/jamanetworkopen.2019.14084

Journal Information: JAMA