If you had to schedule surgery, what day of the week would you pick? Or rather, what day wouldn’t you pick? It might seem like a minor detail, but research suggests it could impact your recovery—or even your survival. Studies have long pointed to a “weekend effect,” where surgeries performed just before or during the weekend lead to higher risks. But new findings challenge this idea. Instead, the real issue may not be the day itself but rather how hospitals manage resources and staffing throughout the week.

In a new study published in JAMA Network Open, researchers analyzed nearly 430,000 surgeries performed in Ontario, Canada. They found that patients who underwent surgery immediately before the weekend had a higher risk of death, complications, and hospital readmission than those operated on just after the weekend. Yet, other studies from different healthcare systems, including Japan and the UK, paint a more complex picture.

The Case Against Friday Surgeries

The Canadian study, led by Dr. Sanjana Ranganathan and colleagues, examined 25 common surgical procedures performed between 2007 and 2019. The findings were stark: patients who had surgery on a Friday had a 5% higher risk of complications within 30 days compared to those who had surgery on a Monday. The risk persisted at 90 days and even a year later. The study accounted for patient health, type of surgery, and hospital resources. Despite this, the pattern remained.

This aligns with prior UK research, which found a 44% higher risk of death for patients undergoing surgery on a Friday compared to a Monday. One proposed explanation is that weekend staffing levels—often lower than during the week—may affect postoperative care. If a complication arises on a Saturday, fewer senior specialists may be available to intervene quickly.

However, in other parts of the world, things were different.

Across the Pacific, a study in Japan examined whether providing full seven-day hospital services—including weekend elective surgeries—could mitigate the weekend effect. The results suggested that while weekend emergency surgeries did carry higher risks, elective surgeries performed on weekends were just as safe as those done during the week.

Conducted at Showa University Koto Toyosu Hospital in Tokyo, the study analyzed 7,442 surgical cases over two years. Researchers found that for emergency surgeries, weekend procedures had significantly higher mortality rates than weekday surgeries (5.5% vs. 2.1%). But for elective procedures, the risk was actually lower on weekends than on weekdays (0.08% vs. 0.23%).

The study’s authors speculated that Japan’s structured approach to weekend staffing helped maintain care standards for planned surgeries. In particular, Japan ensured specialist availability even on Saturdays and Sundays. This suggests that hospital management strategies, rather than the mere timing of surgery, is a main player in determining patient outcomes.

What You Should Take From This

For elective procedures, the latest evidence suggests that the day of the week may not be as critical as once feared—provided the hospital is well-staffed and prepared. But for emergency surgeries, the weekend still appears to pose risks, especially in healthcare systems with reduced weekend resources.

Should patients avoid Friday surgeries? In some systems, particularly in Canada and the UK, the data suggests it might be worth considering. Meanwhile, in Japan, the seven-day service model appears to offer a buffer against the weekend effect. In other countries… it’s hard to say

Ultimately, the question of whether timing affects surgical outcomes is not a medical issue but rather a policy one. If weekend staffing shortages drive worse outcomes, the answer may not be rescheduling surgeries—but rethinking how hospitals allocate resources across the entire week.