Shedding Light on Depth: A Meta-analysis of Light Versus Deep Anaesthesia and Postoperative Neurocognitive Outcomes in Elderly Surgical Patients

Postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) are common and serious complications in elderly surgical patients, especially after prolonged procedures. Recent evidence suggests that the depth of anaesthesia may influence the risk of these adverse outcomes. This meta-analysis examined whether light versus deep anaesthesia affects the incidence of POD and POCD, as well as recovery measures such as time to post-anaesthesia care unit (PACU) discharge and length of hospital stay in elderly patients. A systematic search identified randomized controlled trials (RCTs) published in English up to May 24, 2025, involving patients aged ≥60 years undergoing major surgery. The outcomes evaluated were POD, POCD, PACU discharge time, and hospital stay. Meta-analyses were conducted using random- or fixed-effects models based on heterogeneity. Eight RCTs with a total of 1,957 elderly patients were included. Light anaesthesia was associated with a significantly lower incidence of POD (OR = 0.52; 95% CI: 0.41-0.66; P < 0.00001; I² = 0%). The incidence of POCD was also reduced with light anaesthesia (OR = 0.55; 95% CI: 0.39-0.77; P = 0.0005; I² = 15%). Time to PACU discharge was shorter under light anaesthesia (mean difference (MD) = -9.43 minutes; 95% CI: -12.87 to -5.99; P < 0.00001; I² = 66%). Although hospital stay showed a trend favouring light anaesthesia (MD = -0.81 days; 95% CI: -1.85 to 0.24; P = 0.13), this result was not statistically significant (I² = 89%). Overall, light anaesthesia appears to reduce the incidence of POD and POCD and is associated with faster early recovery in elderly surgical patients. The observed trend toward shorter hospital stays did not reach significance. These findings indicate potential benefits of lighter anaesthetic strategies, though they should not be interpreted as evidence of direct causation, as other factors such as anaesthetic drug type and surgical invasiveness may also contribute.