Clinical muscle mass-related biomarkers that predict mortality in older patients with community-acquired pneumonia

OBJECTIVE: Community-acquired pneumonia (CAP) is associated with elevated morbidity and mortality, and it usually occurs in older adults. Our goal here was to assess the efficacies of muscle mass-related biomarkers, such as, aspartate transaminase/alanine transaminase (AST/ALT) and creatinine/cystatin C*100 (Cr/CysC*100), in predicting 1-, 2-, and 3-year mortalities of older CAP patients. METHODS: Design: Retrospective cohort study. Setting and Participants: A teaching hospital in western China. Hospitalized CAP patients, aged≥60 years. We separated patients into a high or low muscle mass group, according to the median AST/ALT and Cr/CysC*100, respectively. We acquired data from medical records and local government mortality databases, as well as telephonic interviews. We analyzed the association between low muscle mass (AST/ALT and Cr/CysC*100) and all-cause mortality at 1, 2, and 3 years in older patients with CAP. RESULTS: We enrolled 606 patients (58.58% male; median age: 81 years) for analysis. The 1-, 2-, and 3-year mortality in older patients with CAP in the low muscle mass group (AST/ALT) was higher than in the high muscle mass group (AST/ALT) (1-year: 51.16% vs. 36.96%, p < 0.001; 2-year: 54.46% vs. 41.25%, p = 0.001; 3-year: 54.79% vs. 42.9%, p = 0.003). Upon adjustment of potential confounding factors, we revealed, using cox regression analysis, that the low muscle mass group (AST/ALT) experienced enhanced mortality risk at the 1-, 2-, and 3-year follow-ups, compared to the high muscle mass group (AST/ALT) (1-year: hazard ratios (HR) = 1.46, 95% confidence interval (CI): 1.13–1.88; 2-year: HR = 1.39, 95% CI: 1.09–1.77; 3-year: HR = 1.35, 95% CI: 1.06–1.72). The 1-, 2-, and 3-year mortality of older CAP patients in the low muscle mass group (Cr/CysC*100) was also higher than the high muscle mass group (Cr/CysC*100) (1-year: 56.29% vs. 31.91%, p < 0.001; 2-year: 60.26% vs. 35.53%, p < 0.001; 3-year: 61.26% vs. 36.51%, p < 0.001). Compared to the high muscle mass group (Cr/CysC*100), the low muscle mass group (Cr/CysC*100) experienced enhanced mortality risk at the 1-, 2-, and 3-year follow ups (1-year: HR = 1.9, 95% CI: 1.46–2.48; 2-year: HR = 1.85, 95% CI: 1.44–2.39; 3-year: HR = 1.85, 95% CI: 1.44–2.37). CONCLUSIONS: Low muscle mass (AST/ALT and Cr/CysC*100) were associated with enhanced 1-, 2-, and 3-year mortality risk in older patients with CAP. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-022-03626-y.