Association between surgical start time and postoperative mortality, morbidity and healthcare utilisation in elective non‐cardiac surgeries: a retrospective, single‐centre study using propensity score matching

Summary Introduction There is limited knowledge regarding the impact of surgical start time on postoperative outcomes in elective non‐cardiac surgery. This study investigated the association between surgical start time and surgical outcomes in elective non‐cardiac surgeries, including mortality; morbidity; and healthcare utilisation. Methods We analysed 291,051 patients who underwent non‐cardiac surgery. Patients were grouped by surgical start time: morning (08:00–13:00) vs. afternoon (13:00–18:00). Restricted mean survival time was calculated to assess survival differences. Outcomes were also stratified by weekday and season. Subgroup analyses evaluated associations between surgical timing and outcomes in high‐risk populations, including older adults. Results After propensity score matching, statistically significant differences were observed between the morning and afternoon groups for 30‐day mortality (0.12% vs. 0.17%, p = 0.015); 1‐year mortality (2.73% vs. 3.36%, p < 0.001); composite complications (5.48% vs. 5.94%, p = 0.003); ICU admissions (5.87% vs. 7.18%, p < 0.001); and intra‐operative transfusions (3.40% vs. 4.10%, p < 0.001). Restricted mean survival time analysis revealed significantly shorter survival times in the afternoon group across all time points. Afternoon surgery was associated with increased risk of 30‐day mortality (adjusted hazard ratio 1.33, 95%CI 1.07–1.66, p = 0.010); 1‐year mortality (adjusted hazard ratio 1.26, 95%CI 1.20–1.32, p < 0.001); composite complications (adjusted odds ratio 1.05, 95%CI 1.01–1.08, p = 0.010); ICU admission (adjusted odds ratio 1.09, 95%CI: 1.06–1.13, p < 0.001); and intra‐operative transfusions (adjusted odds ratio 1.27, 95%CI 1.21–1.33, p < 0.001). Subgroup analysis indicated that the impact of surgical start time on outcomes was more pronounced in high‐risk patients and also varied significantly depending on the type of surgery. Discussion Surgical start timing was an independent risk factor for increased short‐ and long‐term postoperative mortality, morbidity and healthcare resource utilisation. The reasons for this are likely to be multifactorial.