Association between surgical admissions, cognition, and neurodegeneration in older people: a population-based study from the UK Biobank.

BACKGROUND: Previous studies have shown that major surgical and medical hospital admissions are associated with cognitive decline in older people (aged 40-69 years at recruitment), which is concerning for patients and caregivers. We aimed to validate these findings in a large cohort and investigate associations with neurodegeneration using MRI. METHODS: For this population-based study, we analysed data from the UK Biobank collected from March 13, 2006, to July 16, 2023, linked to the National Health Service Hospital Episode Statistics database, excluding participants with dementia diagnoses. We constructed fully adjusted models that included age, time, sex, Lancet Commission dementia risk factors, stroke, and hospital admissions with a participant random effect. Primary outcomes were hippocampal volume and white matter hyperintensities, both of which are established markers of neurodegeneration, and exploratory analyses investigated the cortical thickness of Desikan-Killiany-Tourville atlas regions. The main cognitive outcomes were reaction time, fluid intelligence, and prospective and numeric memory. Surgeries were calculated cumulatively starting from 8 years before the baseline evaluation. FINDINGS: Of 502 412 participants in the UK Biobank study, 492 802 participants were eligible for inclusion in this study, of whom 46 706 underwent MRI. Small adverse associations with cognition were found per surgery: reaction time increased by 0·273 ms, fluid intelligence score decreased by 0·057 correct responses, prospective memory (scored as correct at first attempt) decreased (odds ratio 0·96 [95% CI 0·95 to 0·97]), and numeric memory maximum correct matches decreased by 0·025 in fully adjusted models. Surgeries were associated with smaller hippocampal volume (ß=-5·76 mm³ [-7·89 to -3·64]) and greater white matter hyperintensities volume (ß=100·02 mm³ [66·17 to 133·87]) in fully adjusted models. Surgeries were also associated with neurodegeneration of the insula and superior temporal cortex. INTERPRETATION: This population-based study corroborates that surgeries are generally safe but cumulatively are associated with cognitive decline and neurodegeneration. Perioperative brain health should be prioritised for older and vulnerable patients, particularly those who have multiple surgical procedures. FUNDING: The Australian and New Zealand College of Anaesthetists (ANZCA) Foundation and the University of Sydney.

Depth of anaesthesia and mortality after cardiac or noncardiac surgery: a systematic review and meta-analysis of randomised controlled trials.

BACKGROUND: Recent randomised controlled trials have failed to show a benefit in mortality by using processed electroencephalography (pEEG) to guide lighter anaesthesia. We performed a meta-analysis of mortality data from randomised trials of pEEG monitoring to assess the evidence of any protective effect of pEEG-guided light anaesthesia compared with deep anaesthesia in adults aged ≥18 yr. METHODS: Our study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. In February 2022, we searched three databases (Cochrane CENTRAL, OVID Medline, EMBASE) for RCTs of pEEG monitoring that provided mortality data at 30 days, 90 days, and/or 1 yr or longer. RESULTS: We included 16 articles from 12 RCTs with 48 827 total participants. We observed no statistically significant mortality reduction with light anaesthesia compared with deep anaesthesia in patients aged ≥18 yr when all studies were pooled (odds ratio [OR]=0.99; 95% confidence interval (CI), 0.92-1.08). This result did not change significantly when analysing mortality at 30 days, 90 days, 1 yr or longer. We observed no mortality benefit for pEEG monitoring compared with usual care (OR=1.02; 95% CI, 0.89-1.18), targeting higher pEEG index values compared with lower values (OR=0.89; 95% CI, 0.60-1.32), or low pEEG index value alerts compared with no alerts (OR=1.02; 95% CI, 0.41-2.52). CONCLUSIONS: pEEG-guided lighter anaesthesia does not appear to reduce the risk of postoperative mortality. The absence of a plausible rationale for why deeper anaesthesia should increase mortality has hampered appropriate design of definitive clinical trials. CLINICAL TRIAL REGISTRATION: CRD42022285195 (PROSPERO).