Applied Cachexia Research, Department of Cardiology, Charité Medical School, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353, Berlin, Germany,
J Cachexia Sarcopenia Muscle. 2012 Dec;3(4):213-7. doi: 10.1007/s13539-012-0089-z.
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. Assessment of muscle strength using tests such as the short physical performance battery test, the timed get-up-and-go test, or the stair climb power test may also be helpful in establishing the diagnosis. Serum markers may be useful when sarcopenia presence is suspected and may prompt further investigations. Indeed, sarcopenia is one of the four main reasons for loss of muscle mass. On average, it is estimated that 5-13 % of elderly people aged 60-70 years are affected by sarcopenia. The numbers increase to 11-50 % for those aged 80 or above. Sarcopenia may lead to frailty, but not all patients with sarcopenia are frail-sarcopenia is about twice as common as frailty. Several studies have shown that the risk of falls is significantly elevated in subjects with reduced muscle strength. Treatment of sarcopenia remains challenging, but promising results have been obtained using progressive resistance training, testosterone, estrogens, growth hormone, vitamin D, and angiotensin-converting enzyme inhibitors. Interesting nutritional interventions include high-caloric nutritional supplements and essential amino acids that support muscle fiber synthesis.
人体肌肉会不断发生变化。50 岁后，肌肉质量以每年 1-2%的速度下降。50 岁至 60 岁之间，肌肉力量每年下降 1.5%，此后每年下降 3%。这些变化的原因包括运动单位的去神经支配以及快速 II 型肌纤维向缓慢 I 型纤维的净转化，从而导致日常生活活动所需的肌肉力量丧失。此外，脂肪会沉积在肌肉中，但这些变化通常不会导致体重下降。一旦老年受试者的肌肉质量低于年轻对照组平均值的 2 个标准差，且步速低于 0.8m/s，即可临床诊断为肌少症。使用短体适能测试、计时起立行走测试或爬楼梯功率测试等测试评估肌肉力量，也有助于确立诊断。当怀疑存在肌少症时，血清标志物可能有用，并可能促使进一步检查。事实上，肌少症是导致肌肉质量下降的四个主要原因之一。平均而言，据估计，60-70 岁的老年人中有 5-13%受到肌少症的影响。80 岁或以上的老年人中，这一数字增加到 11-50%。肌少症可能导致虚弱，但并非所有肌少症患者都虚弱——肌少症的发病率是虚弱的两倍。多项研究表明，肌肉力量减弱的受试者跌倒风险显著增加。肌少症的治疗仍然具有挑战性，但使用渐进式抗阻训练、睾酮、雌激素、生长激素、维生素 D 和血管紧张素转换酶抑制剂已取得有前景的结果。有趣的营养干预措施包括高热量营养补充剂和支持肌纤维合成的必需氨基酸。
