An overview of sarcopenia: facts and numbers on prevalence and clinical impact

Human muscle undergoes constant changes. After about age 50, muscle mass decreases at an annual rate of 1-2%. Muscle strength declines by 1.5% between ages 50 and 60 and by 3% thereafter. The reasons for these changes include denervation of motor units and a net conversion of fast type II muscle fibers into slow type I fibers with resulting loss in muscle power necessary for activities of daily living. In addition, lipids are deposited in the muscle, but these changes do not usually lead to a loss in body weight. Once muscle mass in elderly subjects falls below 2 standard deviations of the mean of a young control cohort and the gait speed falls below 0.8 m/s, a clinical diagnosis of sarcopenia can be reached.…