Christopher Wallis from 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 — the outcomes of surgeries performed before the weekend were significantly worse than those performed after them. The analysis included almost 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 processing of the data was performed using multivariable generalized estimating equations with adjustments for confounding factors. The results were published in the journal JAMA Network Open.
46.5 percent of the participants had surgery immediately before the weekend, the rest immediately after. The composite outcome of death, complications, and rehospitalization was 5 percent more likely in the first group at 30 days after the intervention and the same amount at one year. The risk of death in such patients was also higher: 9 percent at 30 days, 10 percent at 90 days, and 12 percent at one year.