Cognitive training (CT) has been shown to reduce the risk of postoperative cognitive dysfunction (POCD) in surgical patients undergoing general anesthesia, but the evidence is controversial. Additionally, whether different timings of CT have diverse effects and which surgical populations benefit most are unclear. To answer these questions, we searched Medline, Embase, Web of Science and Cochrane Library through July 18, 2022, for randomized controlled trials (RCTs) of CT in surgical patients with general anesthesia reporting cognitive outcomes, and found 13 studies including 989 patients. Pooled analysis showed that CT could significantly reduce the incidence of POCD (k=7, RR=0.52, 95% confidence interval (CI)=[0.34–0.78]), especially for the noncardiac surgery population (k=4, RR=0.43 [0.29–0.63], P<0.01, I2 =0%). The pooled RRs for preoperative CT and postoperative CT were both low and statistically significant, while that for perioperative CT was not (k=2, RR=0.42 [0.25–0.70], P<0.01, I2=0% vs k=4, RR=0.43 [0.28–0.67], P<0.01, I2=0% vs k=1, RR=1.44 [0.69–3.01], P=0.34, I2=0%). Small to moderate effects were found for executive function, speed, language and verbal memory, while no statistically significant effects were found for postoperative delirium (POD), global cognition, working memory, and psychosocial functioning, including depressive symptoms and anxiety symptoms. Although RCT evidence remains sparse, current evidence suggests that preoperative and postoperative CT may help reduce the incidence of POCD, particularly in the noncardiac surgery population, and improve specific cognitive domains in surgical patients. This intervention therefore warrants longer-term and larger-scale trials to examine the effects on the risk of POD and application to the cardiac surgery population.
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