Nancy A. Melville

October 07, 2013

BALTIMORE — Older men with sarcopenia and osteopenia or osteoporosis have a nearly 3-fold higher fracture risk than is seen with either condition alone, according to new research presented here at the American Society of Bone and Mineral Research 2013 Annual Meeting.

The work is the first to examine the combination of sarcopenia — the age-related loss of skeletal muscle mass — and low bone mass on fracture risk, and the findings underscore the need to consider sarcopenia, particularly in men, when assessing patients' fracture risk, said Didier Chalhoub, MD, MPH, a researcher in the University of Pittsburgh's Department of Epidemiology, who reported the findings.

"If other studies find similar results, we strongly suggest a paradigm shift of adopting a more holistic approach and assessing the risk of fractures by looking not only at the bones but at the muscles," he said.

Robert Marcus, MD, a retired Stanford University bone specialist, seconded the need to look beyond bones in considering fracture risk.

"The take-home message is that doctors need to pay as much attention to muscle function, which is a powerful determinant for falls, which in turn are a precipitant for hip fractures," he told Medscape Medical News. "Unfortunately, right now the state of the art doesn't really allow the practicing physician too many options in terms of [evaluating for sarcopenia]," he noted.

"Doctors could perhaps incorporate using grip strength — that's not expensive and it's easy to learn. But you certainly can't do muscle biopsies on everyone, so I don't know if it's ready for prime time in the primary-care office."

Understanding the Role of Sarcopenia in Fracture

Sarcopenia has only in recent years gained an operational definition, with well-described risk factors including age, gender, and levels of physical activity. Effective management strategies are now being developed, including resistance exercise, with a possible additional role for nutritional intervention. Sarcopenia is also currently a major focus for drug discovery, although there remains debate about the best primary outcome measure for trials, and various promising avenues to date have proved unsatisfactory.

In an effort to better understand its role in the basic issue of fracture risk, Dr. Chalhoub and his colleagues evaluated data on 1204 women with a mean age of 77.6 years from the Study of Osteoporotic Fractures (SOF) and 5729 men with a mean age of 73.7 years from the Osteoporotic Fractures in Men (MrOS) study.

Patients' bone-mineral density (BMD) and appendicular lean mass (ALM) were assessed by dual-energy X-ray absorptiometry (DXA), and grip strength and walking speed over 6 m were also measured.

Sarcopenia was defined according to the European Working Group on Sarcopenia in Older Persons, which factors in slowness (gait speed = 0.8 m/s); weakness (grip strength <30 kg men, <20 kg women); and low lean mass (ALM corrected for height and total fat mass; <20%, sarcopenic).

Osteopenia or osteoporosis was defined as a femoral neck T-score of less than 2.5.

According to those definitions, patients were categorized into 4 groups: normal BMD and lean mass (n = 3398 men, 312 women); sarcopenia with normal BMD (n = 153 men, 45 women); osteopenia/osteoporosis and no sarcopenia (n = 1972 men, 621 women); and sarcopenia with osteopenia/osteoporosis (n = 205 men, 139 women).

At baseline, the men with sarcopenia had significantly lower grip strength, compared with nonsarcopenic men, and the men with sarcopenia had higher rates of impairment, were less physically active, and had poorer overall health and higher comorbidities than nonsarcopenic men.

Women followed similar trends, but while grip strength was lower in sarcopenic women than nonsarcopenic, the difference between them was less dramatic than that seen between men with and without sarcopenia.

Speed of Decline of Muscle Mass in Men May Be Factor

The researchers then looked at the radiographic reports over 8 years for women and 9 years for men and compared the incidence of age-adjusted nonspine fractures across the 4 groups.

Among men, the risk for nonspine fractures in the normal group was about 10 per 1000, compared with 15.7 among those with sarcopenia; 17.4 in the osteopenia/osteoporosis group; and as high as 30.5 in the group with both sarcopenia and low bone mass.

Among women, the nonspine-fracture risk in the normal group was about 11 per 1000 and around 17.3 in the sarcopenic group. The rates were similar however, at about 32 per 1000 in the osteopenia/osteoporosis group and the group with both sarcopenia and low bone mass.

In addition, the men in the sarcopenia/low-bone-mass group had greater decreases in total hip-bone density compared with those in the low-bone-mass-only and normal groups.

"Sarcopenia was an independent risk factor for fractures in men, and we believe this was important because these men had higher rates of impairment, poor health, and lower activity, and most important they had a much lower grip strength compared with nonsarcopenic men," Dr. Chalhoub observed.

One reason that men, but not women, had an increased fracture risk when sarcopenia was present could have to do with the degree of muscle-mass reduction, he hypothesized. "Although men at baseline had higher muscle mass, the rate of decrease is much greater and more rapid than in women. So, while the rate of muscle mass is lower in women, they have less of a decrease than men."

And although the study didn't evaluate risk factors for sarcopenia, he suggested that the reduction in testosterone as men age could play a role.

Dr. Chalhoub and Dr. Marcus have reported no relevant financial relationships.

American Society of Bone and Mineral Research. Abstract 1026, presented October 5, 2013.


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