Sarcopenia, a loss of muscle mass often associated with weakness, is a commonly recognized cause of disability in older people. However, without consensus on ways to specifically measure this condition, the development of interventions for sarcopenia has been challenging. Now, a team of researchers proposes a comprehensive set of diagnostic criteria, presented April 15, 2014, in six special articles in the Journals of Gerontology: Medical Sciences.
The proposed criteria are from the Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium Sarcopenia Project, which includes scientists and grantees from the National Institute on Aging (NIA) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases at NIH, along with other partners in government, academia and the private sector.
“We know that compromised function related to low muscle mass and weakness can significantly impair the ability of older people to walk and to live independently,” said NIA Director Richard J. Hodes, M.D. “These criteria, the first based on evidence from large population studies of older people, offer a way to better define and measure this problem so that we can eventually assess the effectiveness of drugs and other interventions for this disabling condition.”
To arrive at the measures, the Sarcopenia Project used existing data sources to identify and standardize criteria for clinically relevant weakness and low lean muscle mass. Researchers pooled data from nine large studies of older people living in the community and analyzed it for grip strength and appendicular lean mass (ALM), which is muscle mass in the arms and legs. The total sample included more than 26,000 participants. The average age of the men was about 75.2 years, and the average age of the women was 78.6 years. Women comprised 57 percent of the sample.
The databases included the Age, Gene/Environment Susceptibility–Reykjavik Study; Boston Puerto Rican Health Study; a series of six clinical trials from the University of Connecticut; Framingham Heart Study; Health, Aging, and Body Composition Study; Invecchiare in Chianti; Osteoporotic Fractures in Men Study; Rancho Bernardo Study; and Study of Osteoporotic Fractures.
Walking speed of less than 0.8 meters (2 feet, 7.5 inches) per second was chosen as the primary outcome because of its strong association with disability and death in other studies. Then, the recommended values for weakness and ALM were paired with this slow walking speed to predict the likelihood of an individual’s disability and death. Weakness was assessed by measuring grip strength, the force applied by the hand to grip an object. ALM was obtained through total body scans measuring bone-free muscle mass in the arms and legs.
The values for a weak grip were less than 26 kilograms (kg) (about 57 pounds) for men and less than 16 kg (about 35 pounds) for women. The values for low lean mass were ALM of less than 19.75 kg (about 43 pounds) in men and ALM of less than 15.02 kg (about 33 pounds) in women. The researchers factored in body mass index (a weight-to-height ratio) to the criteria as well, to account for effects of obesity.
“The Sarcopenia Project investigators’ extensive analyses of the pooled data resulted in some intriguing insights,” said Luigi Ferrucci, M.D., Ph.D., NIA scientific director and a co-author on five of the papers. “We found that the odds for impaired mobility were generally greater for those with weakness than for those with low muscle mass. These differences must be evaluated in additional studies to determine whether they identify the groups of older adults who are likely to benefit from interventions to maintain or improve mobility.”
The criteria will need to be further tested and validated. The investigators noted that the pooled dataset included primarily healthy older people, with relatively few chronic health issues, who lived in the community. Additional research is needed in more vulnerable older populations where disability rates are higher and comorbid factors such as impaired cognition, osteoarthritis, pain and disuse atrophy more common.
The sixth article by Rosaly Correa-de-Araujo, M.D., Ph.D., and Evan Hadley, M.D., of NIA’s Division of Geriatrics and Clinical Gerontology, proposes the term, “Skeletal Muscle Function Deficit,” to describe the variety of muscular conditions that contribute to clinically meaningful mobility impairment, such as that described by the Sarcopenia Project. They note that the term embraces the evolving concepts of sarcopenia and other age-related muscle dysfunctions and has the potential to provide a framework for developing diagnostic categories that may be useful for both research and clinical practice.
Studenski, Stephanie A., et al., The FNIH Sarcopenia Project: Rationale, Study Description, Conference Recommendations, and Final Estimates. J Gerontol A Biol Sci Med Sci. Published online April 15, 2014. doi:10.1093/gerona/glu010.
Alley, Dawn E., et al., Grip Strength Cutpoints for the Identification of Clinically Relevant Weakness. J Gerontol A Biol Sci Med Sci. Published online April 15, 2014. doi:10.1093/gerona/glu011.
Cawthon, Peggy M., et al., Cutpoints for Low Appendicular Lean Mass That Identify Older Adults With Clinically Significant Weakness. J Gerontol A Biol Sci Med Sci. Published online April 15, 2014. doi:10.1093/gerona/glu023.
McLean, Robert R., et al., Criteria for Clinically Relevant Weakness and Low Lean Mass and Their Longitudinal Association With Incident Mobility Impairment and Mortality: The Foundation for the National Institutes of Health (FNIH) Sarcopenia Project. J Gerontol A Biol Sci Med Sci. Published online April 15, 2014. doi:10.1093/gerona/glu012.
Dam, Thuy-Tien, et al., An Evidence-Based Comparison of Operational Criteria for the Presence of Sarcopenia. J Gerontol A Biol Sci Med Sci. Published online April 15, 2014. doi:10.1093/gerona/glu013.
Correa-de-Araujo, Rosaly and Hadley, Evan. Skeletal Muscle Function Deficit: A New Terminology to Embrace the Evolving Concepts of Sarcopenia and Age-Related Muscle Dysfunction. J Gerontol A Biol Sci Med Sci. Published online April 15, 2014. doi:10.1093/gerona/glt208.
About the National Institute on Aging (NIA): The NIA leads the federal government effort conducting and supporting research on aging and the health and well-being of older people. The Institute’s broad scientific program seeks to understand the nature of aging and to extend the healthy, active years of life. For more information on research, aging and health, go to www.nia.nih.gov .
About the Foundation for the NIH (FNIH): The FNIH creates and manages alliances with public and private institutions in support of the mission of the NIH, the world’s premier medical research agency. The Foundation works with its partners to accelerate key issues of scientific study and strategies against diseases and health concerns in the United States and across the globe. The FNIH organizes and administers research projects; supports education and training of new researchers; organizes educational events and symposia; and administers a series of funds supporting a wide range of health issues. Established by Congress in 1996, the FNIH is a not-for-profit 501(c)(3) charitable organization. For additional information about the FNIH, please visit www.fnih.org .
About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical and translational medical research, and is investigating the causes, treatments and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov .
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