Association between preoperative physical exercise and postoperative delirium in silent brain infarction

BACKGROUND: Evidence is lacking regarding the association between preoperative leisure-time physical activity and postoperative delirium occurrence in high-risk populations with concomitant silent brain infarction. OBJECTIVE: This study aimed to use causal inference models to explore the potential association between leisure-time physical activity before surgery and postoperative delirium occurrence. DESIGN: Multicentre prospective cohort study. SETTINGS: Four tertiary care medical centres in China from March 2024 to February 2025. PARTICIPANTS: This study enrolled 2512 adult patients with asymptomatic cerebral infarction between 2024 and 2025 who were scheduled to undergo elective noncardiac and nonneurological surgery under general anaesthesia. EXPOSURES: Preoperative leisure-time physical activity assessed using the Godin Leisure-Time Exercise Questionnaire. MAIN OUTCOME MEASURE: Incidence of postoperative delirium within 7 days postoperatively as identified by the Chinese version of the 3-Minute Diagnostic Confusion Assessment Method. RESULTS: The unadjusted postoperative delirium incidence was 28.4% in the low physical activity group versus 17.5% in the moderate-to-vigorous physical activity group, with an unadjusted odds ratio (95% confidence interval) of 0.53 [95% confidence interval (CI) 0.43 to 0.66). After adjustment for age, sex, and other confounders, the predicted incidence in the low physical activity group decreased to 24.1%, whereas that in the moderate-to-vigorous physical activity group increased to 18.6%, yielding a weighted odds ratio of 0.72 (95% CI 0.58 to 0.90). The postoperative delirium severity scores in both adjusted and unadjusted models markedly declined during postoperative days 1-3, then stabilised. The multivariable model identified significant positive associations between postoperative delirium severity and advanced age (β = 0.064; 95% CI 0.032 to 0.096). Surgery time and intra-operative hypothermia are significant mediators. CONCLUSION AND RELEVANCE: Preoperative moderate-to-vigorous physical activity is associated with a significantly reduced risk of postoperative delirium in patients with silent brain infarction. Findings indicate that postoperative delirium severity is self-limiting, with symptoms resolving rapidly within 3 days after surgery. Surgery time and intra-operative hypothermia are significant mediating factors in this association.