Preoperative cognitive training for the prevention of postoperative delirium and cognitive dysfunction: a systematic review and meta-analysis

Postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) are associated with major morbidity and mortality after surgery. This systematic review and meta-analysis determined whether preoperative cognitive training could reduce POD and POCD in patients undergoing elective surgery. Eligible randomized controlled trials were identified from CENTRAL, MEDLINE, EMBASE, Scopus, Web of Science, and CINAHL databases from inception to April 30, 2024. Two independent reviewers extracted data on trial characteristics and risk of bias for each trial. We rated the quality of reporting of cognitive training interventions using the template for intervention description and replication (TIDieR) and evaluated the overall certainty (quality) of evidence using The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. Random-effects models were used to summarize the treatment effect of cognitive training. Post hoc trial sequential analyses (TSA) were performed for POD and POCD to differentiate between "no evidence of effect" and "evidence of no effect." Seven trials (four high risk and three unclear risk of bias) involving 864 participants (mean or median age between 66 and 73 years old) were considered eligible and subject to meta-analysis. The quality of reporting cognitive training interventions was fair to moderate. Most cognitive prehabilitation programs were home-based, unsupervised, computerized interventions requiring 2.3-10 h over 1-4 weeks before surgery. Cognitive prehabilitation did not reduce POD (risk ratio [RR] 0.82, 95% confidence interval [CI] 0.57-1.18; I = 30%; low certainty of evidence in five trials) or early POCD after surgery (RR 0.93, 95% CI 0.58-1.49; I = 67%; very low certainty of evidence in four trials) compared to usual care. Nonetheless, TSA suggested that the sample sizes were insufficient to exclude the effectiveness of preoperative cognitive training in reducing POD or POCD. The participants' compliance rate was either not reported or mostly below 70%. Current evidence is insufficient to determine the beneficial effect of preoperative cognitive training on POD or POCD. Given the well-established benefits of long-term cognitive training on cognition in the elderly, the design of future cognitive prehabilitation trials should be adequately powered and incorporated with strategies to improve patient compliance.