Even mild physical activity can cut fracture risk in older women

While it is nothing new that greater total physical activity is associated with a lower risk of hip fracture in older women, the finding that such association holds even with mild activity and walking is novel and comes with important public health implications, according to the Women’s Health Initiative (WHI) study.

“Lower-intensity activities are more easily adopted by older individuals and should be recommended when such activity is not contraindicated,” said the researchers. “If other studies confirm our results showing that light-intensity activity is associated with fracture benefit, there could be basis for a future guideline recommendation.”

Over a median follow-up of 14 years among 77,206 postmenopausal women (mean age 63.4 years), a first incident fracture occurred in 25,516 (33.1 percent) women. [JAMA Netw Open 2019;2:e1914084]

Women who reported having a higher total physical activity (>17.7 metabolic equivalent [MET] hours/week) had a significantly lower risk of hip fracture compared with women who did not engage in physical activity (hazard ratio [HR], 0.82; p for trend <0.001).

The risk of hip fracture was reduced even with mild activity (HR, 0.82; p for trend=0.003), walking (>7.5 MET hours/week; p for trend=0.01), and yard work (HR, 0.90; p for trend=0.04) compared with no activity.

In addition, there were significant inverse associations between hip fracture risk and moderate to vigorous activity (MVPA; HR, 0.88; p for trend=0.002).

Besides the hip, mild activity also appeared to have a protective effect against clinical vertebral fracture (HR, 0.87; p for trend=0.006) and total fractures (HR, 0.91; p for trend <0.001).

“Because hip and vertebral fractures occur frequently in older women, even a modest protective association with physical activity could account for a meaningful number of averted fracture cases and related complications within the population,” the researchers pointed out on the public health implications of the findings.

In contrast, higher total activity was associated with an increased risk of knee fracture compared with no activity (HR, 1.26; p for trend=0.08). Also, the greater the levels of MVPA, the higher the risk of wrist or forearm fracture (HR, 1.09; p for trend=0.004).

“Women capable of doing MVPA may be more functional and more likely to break a fall with outstretched hands, which could account for the higher prevalence of wrist and forearm fractures associated with MVPA in the present study,” explained the researchers on the positive association.

“[The study also] extended understanding by demonstrating associations of physical activity with fractures at other sites previously studied infrequently or not at all,” they added.

Similarly, those who spent >9.5 hours/day being sedentary — defined as time spent sitting or lying down but not asleep — had a higher risk of total fracture than those who were less sedentary (<6.5 hours/day of sedentary time; HR, 1.04; p for trend 0.01).  

However, the researchers found that engaging in greater levels of total activity appeared to mitigate to some extent the total fracture risk linked to sedentary behaviour.

According to the 2018 revised physical activity guidelines by the US Department of Health and Human Services, regular MVPA is recommended for maintaining health in adults.

“It has been suggested that even mild (ie, light) activity could be beneficial for older adults … [but] there has been insufficient evidence available [to date] to support recommending lighter intensity activities as part of public health guidelines,” the researchers noted.

“If confirmed, future recommendations on fracture prevention in postmenopausal women should promote light physical activity, especially in those who are frail and unable to safely engage in more intense activities,” they urged.