Christopher Wallis of the University of Toronto and colleagues from Canada and the United States conducted a large retrospective cohort study and confirmed the existence of a "weekend effect" in surgery: outcomes of surgeries performed before the weekend were significantly worse than those performed after. The analysis included nearly 430,000 patients (mean age 58.6 years; 62.8 percent women) who underwent one of the 25 most common surgeries from January 2007 to December 2019 in Ontario. Statistical analysis was performed using multivariable generalized estimating equations adjusted for confounding factors. The results were published in JAMA Network Open.
46.5 percent of participants underwent surgery immediately before the weekend, while the rest underwent surgery immediately after. The composite outcome of death, complications, and readmission was 5 percent more likely in the first group at 30 days postoperatively and 5 percent more likely at one year. The risk of death in these patients was also higher: 9 percent at 30 days, 10 percent at 90 days, and 12 percent at one year.
