Prevalence of Sarcopenia-Related Muscle-Health Phenotypes in Patients With Severe Mental Illness: A Systematic Review...

Severe mental illness (SMI) is associated with substantial physical morbidity and premature mortality, yet muscle health has received limited attention in this population. This systematic review and meta-analysis aimed to estimate the prevalence of sarcopenia-related muscle-health phenotypes and to synthesize evidence on impaired muscle health in individuals with SMI. A comprehensive search of PubMed, Cochrane Library, Scopus, and Web of Science was conducted up to February 2026. Eligible studies included patients with SMI and reported sarcopenia or related conditions based on consensus criteria or clearly defined operational definitions. Study selection, data extraction, and risk of bias assessment were conducted following standardized procedures. A random-effects meta-analysis of proportions was performed. Ten studies involving 2210 participants were included; all studies were conducted in China, Japan, or Turkey. Most studies included patients with schizophrenia-spectrum disorders, whereas only one study included individuals with bipolar disorder. The exploratory pooled prevalence of sarcopenia-related muscle-health phenotypes was 43.6% (95% confidence interval: 30.3%-58.2%), with very high heterogeneity and a wide prediction interval. Therefore, this estimate should not be interpreted as a clinically precise prevalence of sarcopenia in SMI. Sensitivity analyses excluding clinically distinct studies and a potentially overlapping sample increased the estimate to 58% (95% confidence interval: 48%-67%), although heterogeneity remained substantial. Exploratory subgroup analyses suggested differences according to country, although this finding may reflect confounding by age distribution, phenotype definition, diagnostic framework, clinical setting, and assessment methods. Overall certainty of evidence was rated as very low due to methodological limitations in prevalence studies, inconsistency, and potential small-study effects. Sarcopenia-related muscle-health phenotypes may represent an underrecognized dimension of physical morbidity in individuals with SMI, although the precision and generalizability of the pooled estimate are limited by high heterogeneity and the use of non-equivalent phenotypes. These findings support broadening physical health assessment beyond cardiometabolic outcomes to include muscle-related impairments and physical frailty.