Dynapenia ups risks of falls, fractures in women with obesity

Reduced muscle strength (dynapenia) is associated with a higher risk of leg and ankle fractures in women with obesity, as shown in a study. Dynapenia also negates the protective effects of obesity on fractures of the wrist, arm, hip, spine, and other bones, thus increasing the risk of falls.

“We have demonstrated that obesity and dynapenia have independent effects on falls risk, but the relationship among obesity, dynapenia, and fracture risk is anatomically site-specific,” the researchers said.

The UK Biobank was used to identify 16,147 women aged 60‒82 years. These participants were then categorized by hand grip strength (HGS; dynapenia status: HGS ≤21 kg) and body weight (body mass index: normal weight, overweight, or obesity).

The researchers used multiple logistic regression models to explore the association among dynapenia and obesity and self-reported falls (previous 12 months), lower extremity fractures, and all other fractures (previous 5 years).

Of the women, 3,793 had a fall, and 1,413 of 15,570 (9.1 percent) eligible participants suffered fall-related fractures. [Obesity 2023;31:496-505]

Irrespective of areal bone mineral density (BMD), obesity (odds ratio [OR], 1.25, 95 percent confidence interval [CI], 1.12‒1.38) and dynapenia (OR, 0.87, 95 percent CI, 0.77‒0.98) independently contributed to an increased risk of lower extremity fracture.

When considering all other fracture sites, however, obesity was found to be protective (OR, 0.77, 95 percent CI, 0.61‒0.96), except in women with low HGS, who had an equivalent fracture risk to those with normal weight (OR, 1.06, 95 percent CI, 0.82‒1.38).

“These findings require validation in prospective analysis and in men, but they may have important clinical implications relating to risk identification and prevention of falls and fractures in a growing population living with overweight and obesity,” the researchers said.

Site-specific fracture

In a recent systematic review, individuals with sarcopenic obesity, or obesity with reduced muscle mass or strength, exhibit a comparable risk of nonvertebral fractures to those with obesity alone, indicating no cumulative effect of sarcopenia on fracture risk. [Obes Rev 2021;22:e13187]

However, available studies reviewed had relatively small sample size and did not consider the site-specific nature of fractures in individuals with obesity, according to the researchers. [Calcif Tissue Int 2016;99:30-42; J Bone Miner Res 2017;32:575-583]

“Our findings are particularly novel because we have used a large cohort and recognized the site-specific fracture risk in people living with obesity,” the researchers said.

“Our results reinforce the evidence regarding the site-specific nature of fractures in people with obesity, with their greater risk of sustaining ankle or leg fractures but a reduced risk of other fractures,” they added. [Am J Med 2011;124:1043-1050; J Bone Miner Res 2012;27:294-300; J Bone Miner Res 2014;29:223-233; J Bone Miner Res 2013;28:1771-1777; J Bone Miner Res 2010;25:292-297]

The mechanism by which dynapenia counteracts the protective effect of obesity on risk of other fractures remains unclear, the researchers noted.

Previous studies found BMD to be a risk factor for fracture, but its measurement is difficult in individuals with obesity due to confounding by body mass and bone size. [J Bone Miner Res 2005;20:1185-1194; J Bone Miner Res 2005;20:1185-1194]