Estimated appendicular skeletal muscle mass using calf circumference and mortality: Results from the aging and longevity study in the Sirente geographic area (ilSIRENTE study)

Objective: Low muscle mass is one of the mediators of numerous complications accompanying malnutrition status and sarcopenia and at the same time may have a greater effect on survival than other clinical characteristics. In this study, we evaluated the impact of low appendicular skeletal muscle (ASM) on all-cause mortality risk over 10 years in older community-dwellers. Design: Prospective cohort study. Setting: Population-based study. Participants: All persons aged 80+ years living in the community of the Sirente geographic area (L'Aquila, Italy) (n = 364). Participants were categorised in low or normal ASM based on the COONUT equation that considered calf circumference, age and gender. Primary outcome: All-cause mortality over 10 years according to the low ASM estimated by calf circumference. Results: Low estimated ASM was identified in 128 participants (37 %). A total of 245 deaths were recorded over 10 years: 110 among participants with low ASM (85.3 %) and 135 among persons with normal ASM (65.1 %; p < 0.001). Participants with low ASM had a higher risk of death than those with normal ASM (HR: 3.38; 95 % CI: 1.93-5.93). This association remained statistically significant after adjusting for a number of potential confounders, such as age, gender, ADL impairment, cognitive impairment, BMI, and plasma CRP and IL6 levels (HR: 1.84; 95 % CI: 1.03-3.28). Conclusions: Our findings show that low estimated ASM by calf circumference is predictive of 10 years mortality in older community-dwellers. The derived equation used in the present study to estimate ASM, based on calf circumference, may be particularly relevant in clinical practice. Hence, in older persons with low ASM, interventions targeting muscle mass may be effective at preventing or postponing negative health outcomes.