A thorough study of 429,691 surgeries in Canada has revealed a worrying statistic: you're around 5 percent more likely to die, experience complications, or need to go back to the hospital if you have your operation just before the weekend, rather than just after.

The study, carried out by a team from institutions across the US and Canada, suggests Friday fatigue affects medical professionals as much as the rest of us. However, there are likely to be multiple factors involved in causing the discrepancy.

While the researchers didn't dig too deeply into the reasons behind these statistics, they do have some ideas about what's happening – and they're calling for more work to be done to make sure standards of care are kept constant across the whole week.

"These findings suggest that patients treated before the weekend are at increased risk of complications, emphasising the need for further investigation into processes of surgical care to ensure consistent high-quality care and patient outcomes," write the researchers in their published paper.

The surgery data was collected over 12 years, and the researchers compiled statistics for outcomes at 30 days, 90 days, and a year after surgery. The benefits of having surgery after the weekend persisted across all these time periods.

Interestingly, the difference between pre-weekend and post-weekend surgeries was less pronounced if it was an emergency procedure. The researchers think this might be because emergency surgeries are less likely to be put off until the next week – meaning the conditions of patients have less opportunity to worsen.

Further research is going to be needed to figure out exactly what's going on here, but given that previous studies have found similar patterns, the underlying causes are most probably many and varied.

"System-level factors, such as staffing differences, service availability, and obstacles with care coordination, likely play a contributing role," write the researchers.

One data point the researchers did refer to was that the surgeons on duty tended to have around three years less experience overall on Friday compared to Monday. This could be a starting point for hospitals looking to provide care that's more consistent over the whole week.

This isn't the only factor that may influence your chance of a successful surgery either. Earlier research has suggested that the risk of death for female patients is significantly higher if the surgeon is male – though the reasons why aren't clear.

Ultimately, surgeons and other health professionals are all committed to doing the best possible job they possibly can for their patients, and identifying patterns like this are helpful in making sure that happens.

"Further study is needed to understand differences in care that may underpin these observations and ensure that patients receive high-quality care regardless of the day of the week," write the researchers.

The research has been published in JAMA Network Open.