肌少症是一個以肌肉量與肌肉功能低下為表現的症候群。肌少症不僅盛行於老年族群，也是導致老年人失能、跌倒、高死亡率與其他許多老年人不良健康狀態的主要危險因子。根據目前國際上的共識，若老人同時有肌肉量低下與身體功能或肌力低下，即可診斷為肌少症。但是對於台灣老人，定義肌肉量低下、身體功能低下與肌力低下的切點仍不清楚。本篇文章整理國際上肌少症診斷之共識及肌少症流行病學研究的發現，更進一步以流行病學研究方法探究台灣老人肌肉量、身體功能(步行速度)與肌力（手握力）的切點，並檢視肌少症的盛行率及其相關因子。我們綜合5個台灣世代研究，蒐集2,867位社區老人的資料，並依國際之共識定義肌肉量(四肢骨骼肌肉量/身高平方)的切點為：低於年輕族群性別分佈的2個標準差，或低於本研究族群中該性別分佈最低的20%。步行速度和手握力的切點定義為低於族群分佈中最低的20%。本研究據此找出了定義台灣老人族群肌少症相關肌肉量、步行速度與手握力的切點，並且以此切點計算本研究族群的肌少症盛行率[介於3.9%(女性2.5%、男性5.4%)以及7.3%(女性6.5%、男性8.2%)之間]，與其他族群相似。年齡較大、身體質量指數(BMI)較低以及自述有心臟病的社區老人較可能罹患肌少症。本研究建議將肌肉量、步行速度與手握力的測量納入老人之周全性健康評估項目，當老人的肌肉量、步行速度與手握力低於以下數值須分別考慮到肌肉量低下、身體功能低下與肌力低下：肌肉量男性7.09kg/m2’女性5.70kg/m2；步行速度男性0.7m/s’女性0.6m/s；手握力男性26kg’女性16kg。

Sarcopenia, a syndrome characterized by loss of skeletal muscle mass and function, is prevalent among older adults and represents a major risk factor of disability, falls, death and other adverse health outcomes. According to current international consensus, diagnosis of sarcopenia requires the presence of low muscle mass and poor physical performance or muscle strength. However, the appropriate cutoff points of the muscle mass, physical performance (usual gait speed), and muscle strength (handgrip strength) in our population remains unclear. Epidemiology of sarcopenia and current international consensus on sarcopenia diagnosis were reviewed. Furthermore, we pooled individual participant data of 2867 community-dwelling older adults from 5 cohort studies to develop cut-off points of muscle mass, gait speed and handgrip strength, and to examine the prevalence of sarcopenia using these cut-off points. According to current international consensus definition, the cut-off point of a skeletal muscle mass index (ASM/ht2) was defined as values two standard deviations below the sex-specific means of a young population or as the 20th percentile of the sex-specific distribution in our study population. The gait speed and handgrip strength cut-off points were defined as the 20th percentile of their population distributions. Applying these cut-off points to our study population, the prevalence of sarcopenia varied from 3.9 % (2.5 % in women and 5.4 % in men) to 7.3 % (6.5 % in women and 8.2% in men) and is comparable to those in other populations. Older age, lower BMI and history of heart disease were each independently associated with sarcopenia. Testing of muscle mass, gait speed and handgrip strength should be included in a comprehensive health assessment for older adults. Older Taiwanese adults could be considered to have low muscle mass, physical performance and muscle strength if muscle mass, gait speed, and handgrip strength fall within the following ranges: muscle mass (ASM/ht2), <7.09 kg/m2 for men and <5.70 kg/m2 for women; gait speed, <0.7 m/s for men and <0.6 m/s for women; and handgrip strength, <26 kg for men and <16 kg for women.