Jacqueline R. Center, MD, PhD, on How Muscle Strength and Performance Influence Osteoporotic Fracture Risk

Findings from a new study¹ shed light on how muscle strength and performance influence and predict fracture risk among elderly men and women.

To find out more about the study and its findings, Endocrinology Consultant reached out to lead study author Jacqueline R. Center, MD, PhD, who is the lab head of Clinical Studies and Epidemiology in the Bone Biology Division at the Garvan Institute of Medical Research in Sydney, Australia. She also is senior staff specialist and deputy director of the Department of Endocrinology at St. Vincent's Hospital and conjoint professor at the School of Medicine at the University of New South Wales in Australia.

ENDO CON: For your study, you and your colleagues assessed the independent contribution of the rate of decline in muscle strength and performance to fracture risk. Can you tell us more about how your study came about and why it’s so important to study this topic?

Jacqueline Center: Although bone density is a good predictor of fracture, the majority of fractures occur in people whose bone density is not in the osteoporotic range. Thus, it is important to look at other risk factors.

We were interested in muscle parameters, particularly given the recent literature around sarcopenia and knowing the importance of falls in fracture risk prediction. However, there are multiple definitions of sarcopenia, and it is a composite of muscle strength and performance and, in some definitions, muscle mass. We were interested in looking at all these individual components and fracture risk in order to tease out what was most important. There is also evidence that muscle function declines with age. There was minimal literature on how this decline affected fracture risk. Thus, we designed this study to examine both decline in muscle strength and performance, as well as baseline muscle strength and performance, on fracture risk.

ENDO CON: Your analysis included 811 women and 440 men aged 60 years or older who participated in the Dubbo Osteoporosis Epidemiology Study and were followed from 2000 to 2018 for incident fracture. How did women vs men fare regarding incident fracture?

JC: Incident fracture is higher in women than men, approximately 2-fold. In this study, as in previous work that we have done, we also found that the incident fracture rates in women were approximately 2-fold that of men. One important point for your readers is that an initial fracture results in an increased risk of a subsequent fracture. Although that was not the focus of this study, we have demonstrated in the past that, though the initial fracture risk of a man is lower than that of a woman, once that man has experienced a fracture, his risk of a subsequent fracture is similar to that of a women (of similar age) who has also experienced a fracture. In other words, once a woman has had an initial fracture, her risk of a subsequent fracture doubles, but once a man has had a fracture, his risk of a subsequent fracture increases 3 to 4 fold.

ENDO CON: What factors affected women’s vs men’s fracture risk? How can health care providers better manage these factors to prevent future fracture risk?

JC: This study focused on the muscle parameters and fracture risk, not overall risk factors per se, though we did adjust for other major risk factors for fracture (ie, age, prior falls, prior fracture, and bone mineral density), as well as other lifestyle factors such as smoking, physical activity, and comorbidities. 

In this study we found that in women, the decline in muscle performance—using a variety of measures such as gait speed, sit-to-stand, and timed get-up-and go—was a significant independent risk for fracture, while in men baseline muscle performance and strength were independent risk factors for fracture. The decline in gait speed was the only muscle performance measure that remained significant for men after accounting for baseline factors.  It is important to note that there were more fractures in women, so some of the insignificance found in the change in muscle parameters in men may be related to a power issue. However, while the decline in muscle performance still played a role in men’s fracture risk, baseline muscle strength and performance appeared to be more important. In women, the decline was the important factor.

It is still speculative why the change in muscle performance seemed more important for women as opposed to a baseline measure in men. In general, the rate of decline of muscle performance appeared somewhat greater for women than men, though the difference would not have reached statistical significance.

Muscle strength and performance are important risk factors for fracture, and patients should be encouraged to remain active and maintain good muscle strength and function. These measures are simple to perform in a physician’s office, and measuring them at baseline and at regular intervals over time may help identify people at increased fracture risk.  

ENDO CON: What other knowledge gaps exist among health care providers regarding fracture risk among older adults?

JC: As mentioned above, it is critical that health care providers are aware that once a man or woman has had a low-trauma fracture, their risk of a second fracture is increased at least 2-fold. Importantly, this increased risk is highest for the first couple of years post fracture before it gradually declines. Thus, it is important to intervene early to prevent the next fracture.

The other main knowledge gap is that most low-trauma fractures in elderly people are associated with an increased mortality. This is not just true for hip and spine fractures but for all proximal fractures (ie, fractures of the ribs, upper arm/humerus, pelvis, femur). Distal fractures (ie, hand, foot, forearm, and ankle) are generally not associated with increased premature mortality. So, a fracture is not a benign process, and underlying osteoporosis needs to be identified and treated. Like subsequent fracture, the greatest mortality risk lies in the first year or 2 post fracture and then gradually declines back to the population mortality rate over the next 5 to 10 years depending on fracture type.

ENDO CON: What is the overall take-home message for endocrinologists, rheumatologists, and other specialists managing patients with high fracture risk?

JC: The main take-home message could be simply framed. Decline in physical performance predicts fracture risk independent of common fracture risk factors such as age and bone density in both elderly women and men. In men, baseline measures of muscle strength and performance were also independently associated with fracture risk and probably more important than the decline. However, a simple measure of lean mass obtained from dual-energy x-ray absorptiometry scans did not predict fracture risk in either women or men.

The gaps pointed out above are also really important to convey, as less than 30% of women and less than 20% of men with osteoporotic fractures worldwide get treated.

Reference:

1. Alajlouni D, Bliuc D, Tran T, Eisman JA, Nguyen TV, Center JR. Decline in muscle strength and performance predicts fracture risk in elderly women and men. J Clin Endocrinol Metabol. 2020;105(9):e3363-e3373. https://doi.org/10.1210/clinem/dgaa414