Abstract / Summary
This systematic review and meta-analysis aimed to analyze the association between fat mass (FM), lean mass (LM), and mortality in older adults (OA). A systematic electronic search was conducted in four databases, followed by an independent duplicate study selection process. The Newcastle–Ottawa Scale (NOS) was used to assess the risk of bias. Statistical analyses were performed using the inverse variance-weighted average method and a random-effects model. Heterogeneity was assessed using the statistical inconsistency index (I 2 ). Forest and funnel plots were generated for pooled analyses and publication bias assessment. The certainty of the evidence was assessed following the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines. We identified 37 cohort studies including 186,789 participants and 24,603 deaths. Thirty reports assessed FM, and 26 assessed LM. For FM index, the pooled hazard ratio (HR) was 0.96 (95% confidence interval [CI]: 0.88, 1.06) with low certainty of the evidence. For LM index, the pooled HR was 0.85 (95% CI: 0.55, 1.30) for all-cause mortality, also with low certainty of the evidence. Overall, the findings across studies were heterogeneous and showed inconsistent associations between body composition (BC) measures and mortality risk. Overall, the findings of this meta-analysis suggest an inconsistent relationship between FM, LM, and mortality risk in OA. Additional studies with longer follow-up durations, larger sample sizes, and comparable BC measurement instruments are needed to clarify these associations. Furthermore, future studies should evaluate specific FM and LM compartments separately to better understand their relationship with mortality. The protocol of this review was registered in PROSPERO CRD420251088143.