Special Article
Sarcopenia: An Undiagnosed Condition in Older Adults. Current Consensus Definition: Prevalence, Etiology, and Consequences. International Working Group on Sarcopenia

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Sarcopenia, the age-associated loss of skeletal muscle mass and function, has considerable societal consequences for the development of frailty, disability, and health care planning. A group of geriatricians and scientists from academia and industry met in Rome, Italy, on November 18, 2009, to arrive at a consensus definition of sarcopenia. The current consensus definition was approved unanimously by the meeting participants and is as follows: Sarcopenia is defined as the age-associated loss of skeletal muscle mass and function. The causes of sarcopenia are multifactorial and can include disuse, altered endocrine function, chronic diseases, inflammation, insulin resistance, and nutritional deficiencies. Although cachexia may be a component of sarcopenia, the 2 conditions are not the same. The diagnosis of sarcopenia should be considered in all older patients who present with observed declines in physical function, strength, or overall health. Sarcopenia should specifically be considered in patients who are bedridden, cannot independently rise from a chair, or who have a measured gait speed less that 1 m/s–1. Patients who meet these criteria should further undergo body composition assessment using dual energy x-ray absorptiometry with sarcopenia being defined using currently validated definitions. A diagnosis of sarcopenia is consistent with a gait speed of less than 1 m·s−1 and an objectively measured low muscle mass (eg, appendicular mass relative to ht2 that is ≤ 7.23 kg/m2 in men and ≤ 5.67 kg/m2 in women). Sarcopenia is a highly prevalent condition in older persons that leads to disability, hospitalization, and death.

Section snippets

Current Consensus Definition

A meeting was convened on November 18, 2009, in Rome, Italy, with the express purpose of arriving at a consensus definition of sarcopenia. Because there has been no true consensus of the appropriate criteria for when an individual may be said to be sarcopenic, recognition of this treatable condition has been lacking. The following definition was the current consensus of the group of scientists and geriatricians who were present at the meeting. In addition, this definition was reviewed by a

Muscle Aging

Over the age span from 20 to 80 years of age, there is approximately a 30% reduction in muscle mass and a decline in cross-sectional area of about 20%.14 This is because of a decline in both muscle fiber size and number.10 There is no consensus on whether there is a selective loss of specific muscle fiber types. Early cross-sectional studies demonstrated a shift in muscle fiber composition with a higher type I/type II fiber ratio with advancing age.11 Larsson12 suggested a preferential loss of

Etiology and Biochemical Basis for Sarcopenia

Sarcopenia is a universal phenomenon with a complex, multifactorial etiology. Many of the potential causes vary by the age of the individual and are summarized in Table 3. The major factors considered to be involved include genetic heritability,41, 42, 43 nutritional status (protein intake, energy intake, and vitamin D status),30, 44, 45, 46, 47, 48 physical activity,49, 50, 51, 52 hormonal changes (declines in serum testosterone and growth hormone),31, 53 insulin resistance,54, 55, 56

Epidemiology

The measurement of muscle mass in humans is difficult, with most of the available methods requiring assumptions that may not always be valid and with variable degrees of accuracy and difficulty. The most direct measurement currently available is urinary creatinine measured over 24-hour periods.67 Other, more indirect, measures include anthropometry,68 bioelectrical impedance, DXA,69 imaging techniques (eg, computed tomography and magnetic resonance imaging), ultrasound, total body potassium,

Sarcopenia and Disability

Sarcopenia is correlated with functional decline and disability.5, 16, 80, 85, 90 Findings are often stronger in men than in women, depending on the indexing method used. Sarcopenia has also been associated with increased mortality,91 although92 weakness has been demonstrated to be a more powerful predictor of mortality in elderly people than muscle mass. In the longitudinal Rancho Bernardo study, sarcopenia was shown to be predictive of falls.81 Janssen93 examined 5036 men and women older than

Conclusion

Sarcopenia represents a major cause of disability and increased health costs in older persons. It is very common, but like most geriatric syndromes, seldom recognized by physicians. Identification of sarcopenic patients at greatest risk can be performed using an easy-to-perform assessment of mobility, such as gait speed and commonly obtained measures of body composition.101 DXA instruments are used to assess bone density for the identification of those at greatest risk for the development of

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    Partial support for this meeting, in the form of travel costs, was provided by GlaxoSmithKline and Abbott, Chiesi, Danone, Merck, Nestlé, Novartis, and Sanofi Aventis.

    From the International Sarcopenia Consensus Conference Working Group Meeting, Rome, Italy, November 18, 2009.

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