Objectives: To examine the definition of sarcopenia in Chinese subjects by relating the value of appendicular skeletal muscle mass (ASM) divided by height squared to physical functional outcomes after 4 years.
Design: Four-year prospective study.
Setting: A Chinese community in Hong Kong SAR China.
Participants: Three thousand one hundred fifty-three community-living men and women aged 65 and older.
Methods: Information collected by questionnaire included demographics, health limitation on activities of daily living (ADLs), self-care, physical activity level, dietary intake, and psychosocial functioning. Measurements included height, weight, grip strength, step length in a 6-minute walk, and body composition. Four-year outcomes for those with ASM in kg per height in meters squared (ASM/ht(2)) less than 2 standard deviations (SDs) and 2 SDs or more below the young adult mean value were compared using analysis of variance and logistic regression, adjusting for potential confounding factors such as age, fat mass, presence or absence of malnutrition, dietary protein and vitamin D intake, comorbidity, and cognitive impairment.
Results: Participants with ASM/ht(2) 2 SDs or more below the young adult mean had lower grip strength and greater limitation in climbing stairs and general ADLs after adjusting for confounding factors. A U-shaped relationship was observed between physical limitation and ASM/ht(2), with increasing physical limitation below or above a range of 7.25 to 6.75 kg/m(2) in men and 6.00 to 6.25 kg/m(2) in women. Values of 5.25 to 6.74 kg/m(2) in women were associated with approximately 30% less risk of functional limitation after 5 years. No clear cutoff was found in men.
Conclusion: Sarcopenia may be defined in terms of a range of values for ASM/ht(2) associated with the lowest risk of future physical limitations. The importance of establishing a quantitative value for the definition of sarcopenia may facilitate future interventional studies using pharmacological or nonpharmacological strategies.