Perioperative risk factors associated with increased incidence of postoperative delirium: systematic review, meta-analysis, and Grading of Recommendations Assessment, Development, and Evaluation system report of clinical literature

Background: Systematic reviews to date have neglected to exclusively include studies using a validated diagnostic scale for postoperative delirium and monitoring patients for more than 24 h. Evidence on current risk factors is evolving with significantly heterogeneous study designs, inconsistent reporting of results, and a lack of adjustment for bias.

Methods: This systematic review and meta-analysis aimed to identify risk factors for postoperative delirium in an adult patient population. Study designs suitable for this review included full-text articles, RCTs, observational studies, cohort studies, and case-control studies. Extracted variables from the 169 (7.4%) selected studies were included in qualitative synthesis, quantitative synthesis, and a postoperative delirium checklist. The 16 variables included in the checklist were selected based on consistency, direction of effect, number of studies, and clinical utility as a reference for future studies.

Results: A total of 576 variables were extracted, but only six were eligible for meta-analysis. Age (mean difference [MD]=4.94; 95% confidence interval [CI], 2.93-6.94; P<0.001), American Society of Anesthesiologists physical status >2 (odds ratio [OR]=2.27; 95% CI, 1.47-3.52; P<0.001), Charlson Comorbidity Index ≥2 (OR=1.9; 95% CI, 1.11-3.25; P=0.0202), and Mini-Mental State Examination (MD=-1.94; 95% CI, -3.6 to -0.27; P=0.0224) were statistically significant.

Conclusions: Risk factors can assist in clinical decision-making and identification of high-risk patients. Literature analysis identified inconsistent methodology, leading to challenges in interpretation. A standardised format and evidence-based approach should guide future studies.