Seven-day services in surgery and the "weekend effect" at a Japanese teaching hospital: a retrospective cohort study.

Background: Hospitals deliver 24-h, 7-day care on a 5-day workweek model, as fewer resources are available on weekends. In prior studies, poorer outcomes have been observed with weekend admission or surgery. The purpose of this study was to investigate the effect of 7-day service at a hospital, including outpatient consultations, diagnostic examinations and elective surgeries, on the likelihood of the "weekend effect" in surgery.

Methods: This was a retrospective cohort study of patients who underwent surgery between April 2014 and October 2016 at an academic medical centre in Tokyo, Japan. The main outcome measure was 30-day in-hospital mortality from the index surgery. The characteristics of the participants were compared using the Mann-Whitney U test or the chi-squared test as appropriate. Logistic regression was used to test for differences in the mortality rate between the two groups, and propensity score adjustments were made.

Results: A total of 7442 surgeries were identified, of which, 1386 (19%) took place on the weekend. Of the 947 emergency surgeries, 25% (235) were performed on the weekend. The mortality following emergency weekday surgery was 21‰ (15/712), compared with 55‰ (13/235) following weekend surgery. Of the 6495 elective surgeries, 18% (1151) were performed on the weekend. The mortality following elective weekday surgery was 2.3‰ (12/5344), compared with 0.87‰ (1/1151) following weekend surgery. After adjustment, weekend surgeries were associated with an increased risk of death, especially in the emergency setting (emergency odds ratio: 2.7, 95% confidence interval: 1.2-6.5 vs. elective odds ratio: 0.4, 95% confidence interval: 0.05-3.2).

Conclusions: Patients undergoing emergency surgery on the weekend had higher 30-day mortality, but showed no difference in elective surgery mortality. These findings have potential implications for health administrators and policy makers who may try to restructure the hospital workweek or consider weekend elective surgery.