Prognostic value of low estimated appendicular skeletal muscle mass in hospitalized older adults: A multicenter prospective observational study

Background: Muscle mass assessment is essential for diagnosing sarcopenia and malnutrition. Various equations for estimating appendicular skeletal muscle mass (ASM) exist. Among these, equations based on basic clinical variables-age, sex, height, and weight-are potentially applicable to a broad range of patients. This study aimed to examine the validity of multiple ASM estimation equations in hospitalized older patients by investigating their associations with adverse outcomes, including mortality and functional decline. Methods: This study used data from the Japan Hospital Acquired Complications project, a multicenter observational study, and included patients aged >= 65 years. ASM was estimated at admission using four previously reported equations. The appendicular skeletal muscle mass index (ASMI) was calculated and classified as low based on predefined cut-off values. Multivariable logistic regression was used to assess association between low ASMI, in-hospital or 3-month post-discharge mortality, and in-hospital Clinical Frailty Scale (CFS) worsening. Results: A total of 1012 patients (mean age 83.9 +/- 6.6 years; 57.4 % female) were analyzed. During hospitalization or within three months after discharge, 109 patients died. Low ASMI, as defined by several equations, was significantly associated with this mortality after adjusting for confounders. Additionally, low ASMI was significantly associated with in-hospital CFS worsening (n = 175), across all equations.