You’re More Likely to Die If You Have Surgery on a Friday

Fatigue is the likely culprit, though there are other factors at play.

March 12, 2025, 2:26pm

If you have a surgery coming up, maybe don’t read this article. Don’t psych yourself out of a medical procedure that could make you healthier. Now, for the rest of you: a study has found that patients who have surgery just before the weekend have a five percent higher risk of complications or death than those who have surgery earlier in the week — and the reason will not shock you at all.

A team of researchers spread across the United States and Canada studied surgeries across 429,691 patients and 25 common surgical procedures in Ontario, Canada. They found that patients who had surgery just before the weekend had a five percent higher risk of complications than those who had surgeries on, say, Monday or Tuesday.

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As you probably guessed, fatigue is the likely culprit, though the study’s authors caution that fatigue isn’t the only factor at play.

The study spans 12 years’ worth of surgeries and tracked patient outcomes at the 30-day mark, the 90-day mark, and one year post-surgery. Across all time frames, surgeries that happened on Fridays had a higher risk of complication.

The study also found that the same could not be said of emergency surgeries. Nonemergency surgeries tend to get kicked down the road for some other day when a patient’s schedule or bank account allows for it, all while a patient’s condition worsens over time, thus heightening the risk when they eventually do get the surgery.

This isn’t the first time a study has found evidence of this so-called “weekend effect.” It’s a known issue that still requires tons more study before anything definitive can be said or done about it.

Right now, researchers say a variety of factors are at play here, with fatigue being just one of them. Service availability and staffing issues also factor into it, as well as scheduling.

The researchers found that the surgeons performing surgeries on Fridays tended to have three years less experience performing surgeries than those working on Mondays. It’s probably best not to make any major life decisions based on this study until this particular observation has been explored more thoroughly by different research teams.