Sarcopenia was first characterized by the slow and progressive loss of muscle mass that is associated with ageing in the absence of any underlying disease or condition.
Subsequently, it was recognized that the key element was a loss of muscle strength (dynapenia) rather than a loss of muscle mass. This has led to a change in the definition to include strength (grip strength) or function (walking speed or distance).
Based on this concept, a number of societies around the world have provided revised definitions (Table below). These definitions have to some extent de-emphasized the importance of ageing, recognizing that sarcopenia has a variety of causes in addition to the physiological effects of aging. The increased interest in this subject is clearly seen by the number of publications published in the last few years compared to previously.
The prevalence from 15% at 65 years to 50% at 80 years in humans, with normal ageing associated with a 1–2% muscle loss beyond the age of 50 years.
Furthermore, the rapidly expanding aging population will only exacerbate the health problems associated with sarcopenia, which directly leads to increased hospitalizations and disability, due in part, by contributing to falls, fractures, and frailty in the elderly.