Skeletal Muscle Mass as a Predictor of Mortality in the Elderly Population

Abstract

Background/Aims: A U-shaped relationship between body mass index (BMI) and mortality has been reported. However, controversy exists as to whether skeletal muscle mass affects mortality in healthy older adults. We evaluated the independent association of BMI or appendicular skeletal muscle mass (ASM) with mortality in elderly people. Methods: A total of 4,261 consecutive subjects older than 65 years who underwent health examinations at Seoul National University Gangnam Center between 2005 and 2009 were included in the analysis. ASM, ASM/height² and ASM/weight were estimated by bioelectrical impedance analysis. Sarcopenia was defined as a relative skeletal muscle mass of 1-2 SD below (class I) or more than 2 SD below (class II) the gender-specific mean for healthy young adults. BMI was grouped into five groups (A-E). Results: During the follow-up period (27.2 ± 13.5 months), 63 subjects died. The subjects who died were significantly older and had a male predominance, increased levels of inflammatory markers and poor nutritional statuses. In a fully adjusted Cox proportional hazards model, BMI was not associated with mortality. However, class I sarcopenia (HR 2.11, 95% CI 1.17 3.79) and class II sarcopenia (HR 3.47, 95% CI 1.62-7.43), defined by ASM/height², were related to all-cause mortality. This association was not observed when sarcopenia was defined by ASM/weight. Class II sarcopenia defined by ASM/height² was associated with cancer-related mortality (HR 5.73, 95% CI 2.22-14.78), but not with cardiovascular mortality (HR 1.56, 95% CI 0.17 14.27). Conclusions: This study indicates that lower skeletal muscle mass is a risk marker for cancer-related and all cause mortality in Korean elderly people. (Korean J Med 2013;85:167-173)