The Association Between COPD, Acute Exacerbations of COPD, and Survival in COPD, with Fat-Free Body Mass Index: A Systematic Review and Meta-Analysis.

Objective: Nutritional status critically influences disease progression and prognosis in chronic obstructive pulmonary disease (COPD). This meta-analysis evaluates the clinical significance of fat-free mass index (FFMI) in COPD prognosis. Methods: A systematic search of PubMed, Embase, Web of Science, Scopus, Ovid, and Cochrane Library (up to December 7, 2024) identified studies comparing FFMI among non-smokers, smokers, COPD patients, and those with acute exacerbations (AE) or mortality. Pooled weighted mean differences (WMD), odds ratios (OR), and hazard ratios (HR) were calculated. Subgroup analyses assessed smoking status and AE sources, with Sensitivity analyses, Egger's test and trim-and-fill method evaluating robustness and publication bias. Results: A pooled analysis including 17 studies involving 4239 patients with COPD revealed that FFMI levels in COPD group were significantly lower than those in control group (WMD = -0.84; 95% CI: -1.63, -0.05). Among COPD patients, no significant difference in FFMI levels was found between AE and non-AE groups (WMD = -1.32; 95% CI: -2.76, 0.11); furthermore, FFMI levels in death group were significantly lower compared to those in survival group (WMD = -1.23; 95% CI: -1.73, -0.74). Notably, FFMI emerged as a critical factor associated with AE occurrence (OR = 0.82; 95% CI: 0.72, 0.95) and survival outcomes (HR = 0.89; 95% CI: 0.86, 0.93) among patients with COPD. Conclusion: Low FFMI is strongly associated with adverse disease progression and poor prognosis in COPD. Tailored interventions targeting nutritional status and body composition may optimize disease management and survival outcomes.