Depressive symptoms as a risk factor for postoperative delirium in older adults: A systematic review and meta-analysis

Background Post-operative delirium (POD) in older adults may be linked to preoperative depression via shared biological pathways. This review synthesizes current findings, highlights methodological gaps and suggests possible pathophysiological mechanisms. Methods Searches across major databases identified eligible studies using validated tools. Standardized mean differences (SMD) and log odds ratios were pooled using random-effects models. Heterogeneity, moderators, and publication bias were assessed using meta-regression and sensitivity analyses in R (metafor package). Results This meta-analysis synthesized findings from 42 studies examining the association between preoperative depression and postoperative delirium (POD), analysing categorical (k = 16) and continuous (k = 26) reported depression data from 9701 patients. Preoperative depression was significantly associated with increased POD risk (OR = 2.50, 95% CI: 1.90–3.28; SMD = 0.49, 95% CI: 0.26–0.73 after outlier removal). Surgical cohort type and depression assessment tools significantly moderated this association. Cognition evaluated by the MMSE did not significantly influence outcomes. Geriatric depression scale (GDS-15) emerged as a consistent predictor, prompting further investigation into optimal cutoff scores for POD risk stratification. Publication bias and heterogeneity were low to moderate. Discussion This meta-analysis confirms preoperative depression, including subclinical symptoms, as a significant predictor of POD. Findings highlight the roles of surgical type and depressive symptoms, suggesting tailored screening and further research into symptom-specific risk pathways. Conclusion Preoperative depression predicts POD. Notably, even GDS-15 scores below the conventional cutoff for depression were associated with increased delirium risk. This finding requires further investigation, including exploration of potential underlying mechanisms such as vascular or other symptom-specific pathways.