Skeletal muscle mass index is independently associated with all‐cause mortality in men: The Nagahama study
Yasuharu Tabara, Kazuya Setoh, Takahisa Kawaguchi, Fumihiko Matsuda
Abstract
Background We aimed to determine if skeletal muscle mass is a predictor of all‐cause mortality and if muscle mass plays a role in the association between body mass index (BMI) and all‐cause mortality in community residents. Methods The study population consists of 3582 elderly (age ≥65 years) adults. The skeletal muscle mass index (SMI) was measured between 2013 and 2016. Men with SMI <7.0 kg/m 2 and women with SMI <5.7 kg/m 2 were considered to have low SMI. All‐cause mortality was determined by reviewing residential registry records (follow‐up duration: 2564 ± 373 days). Results The mortality rate of the low SMI group was significantly higher than that of the normal SMI group in men (191.3 vs. 93.0 per 10 000 person‐years, P < 0.001), but not in women ( P = 0.191). In Cox proportional hazard analysis adjusted for possible covariates, the group differences remained significant (hazard ratio = 1.82, P = 0.011). The results were similar when individuals who died within 1 year of follow‐up were excluded from the analysis ( P = 0.015). Cubic splines revealed that SMI <6.9 kg/m 2 is a risk factor of all‐cause mortality in men. BMI was found to be significantly associated with all‐cause mortality in men ( P = 0.010), but not in women ( P = 0.288); however, the association disappeared after adjustment for SMI ( P = 0.163). Conclusion SMI <6.9 kg/m 2 is a risk factor of all‐cause mortality in men but not in women. SMI underlies the relationship between BMI and all‐cause mortality. Geriatr Gerontol Int 2022; 22: 956–960 .