• Bheeshma Ravi, Daniel Pincus, Stephen Choi, Richard Jenkinson, David N Wasserstein, and Donald A Redelmeier.
• Division of Orthopaedic Surgery, Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
• JAMA Netw Open. 2019 Feb 1; 2 (2): e190111.

ImportancePostoperative delirium in older adults receiving hip fracture surgery is associated with morbidity and increased health care costs, yet little is known of potential modifiable factors that may help limit the risks.ObjectiveTo use population-wide individual-level data on the duration of hip fracture surgery to determine whether prolonged surgical times and type of anesthesia are associated with an increased risk of postoperative delirium.Design, Setting, And ParticipantsThis retrospective population-based cohort study analyzed patients aged 65 years and older receiving hip fracture surgery between April 1, 2009, and March 30, 2017, at 80 hospitals in Ontario, Canada. Generalized estimated equations with logistic regression analysis were used to determine the relationship between procedure duration, type of anesthesia, and the occurrence of postoperative delirium. Restricted cubic splines were also generated to visualize this relationship. Data analysis was conducted from July to October 2018, revision in January 2019.ExposureSurgery duration, measured as the total time in the operating room.Main Outcomes And MeasuresA diagnosis of postoperative delirium during hospitalization.ResultsAmong 68 131 patients with surgically managed hip fracture (median [interquartile range] age, 84 [78-89] years; 72% women) identified, 7150 patients experienced postoperative delirium. In total, 26 853 patients (39.4%) received general anesthesia. Receiving general anesthesia was associated with a slightly higher rate of postoperative delirium compared with not receiving general anesthesia (2943 [11.0%] vs 4207 [10.2%]; P = .001). The risk for delirium increased with increased surgical duration-every 30-minute increase in the duration of surgery was associated with a 6% increase in the risk for delirium (adjusted odds ratio, 1.06; 95% CI, 1.03-1.08; P < .001). Prolonged surgical duration was associated with a higher incidence of postoperative delirium, and the risk was higher was in patients who had received general anesthesia (adjusted odds ratio, 1.08; 95% CI, 1.04-1.12; P < .001) than in those patients who did not receive GA (adjusted odds ratio, 1.04; 95% CI, 1.01-1.08; P = .01).Conclusions And RelevanceAmong older adults receiving hip fracture surgery, both an increased duration of surgery and receiving a general anesthetic were associated with an increased risk for postoperative delirium.

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