According to research, women who are operated on by a male surgeon are much more likely to die, experience complications, and be readmitted to the hospital than women who are operated on by a female surgeon.

According to a study of 1.3 million patients, women are 15% more likely to have a bad outcome and 32% more likely to die when the surgery is performed by a man rather than a woman.

The findings have sparked a debate about how surgery in the UK remains a hugely male-dominated field of medicine, with claims that “implicit sex biases” among male surgeons may help explain why women are at such greater risk when they have an operation.

“In our 1.3 million patient sample involving nearly 3,000 surgeons, we discovered that female patients treated by male surgeons had a 15% higher risk of poor outcomes than female patients treated by female surgeons,” said Dr. Angela Jerath, an associate professor and clinical epidemiologist at the University of Toronto in Canada and a co-author of the study.

The research was published in the medical journal JAMA Surgery.

“These results are concerning,” Jerath added, “because there should be no sex difference in patient outcomes regardless of the surgeon’s sex.”

Jerath and her colleagues examined the medical records of 1,320,108 Ontario patients who had 21 common surgical procedures performed by 2,937 surgeons between 2007 and 2019. They ranged from hip and knee replacements and weight loss surgery to appendix or gall bladder removal and more complicated operations like a heart bypass, aneurysm repair, and brain surgery.

The sex of each patient and details about how their procedure went, as well as the sex of the surgeon who performed it, were recorded for each of the 1.3 million operations studied.

They discovered that men who underwent surgery had the same outcomes whether their surgeon was male or female. Women, on the other hand, had better outcomes if the procedure was performed by a female surgeon rather than a male surgeon. There were no gender differences in how men and women were operated on by a female surgeon.

While “there are some excellent male surgeons who consistently have good outcomes,” Jerath added, “what is concerning is that this analysis does signal some real difference between male and female surgeons overall where practice can impact general patient outcomes.”

According to the researchers, this is the first study of its kind to look at the relationship between the gender of the patient, the gender of their surgeon, and the outcomes of surgery. They looked at three types of “adverse postoperative outcome”: death, hospital readmission, and complications within 30 days.

They discovered that for women, treatment by a male surgeon was associated with a 15% higher likelihood of a poor outcome than treatment by a female surgeon. Men, on the other hand, experienced no differences in treatment whether they were treated by a male or female surgeon.

Similarly, women who had surgery performed by a male surgeon had a 32% higher risk of death than those who had surgery performed by a female surgeon. For example, while 1.4 percent of women who had a cardiothoracic operation performed by a male surgeon died, only 1% died when performed by a female surgeon. While 1.2 percent of women who underwent either type of operation with a male surgeon died, that proportion was much lower – 0.9 percent – among those whose surgeon was female, giving a 33 percent higher risk of death.

Overall, female patients also had a 16% greater risk of complications and an 11% greater risk of readmission and were 20% more likely to have to stay in hospital longer.

Across many of the 21 types of surgery studied, women had a higher risk of death, readmission, or complications when the operation was performed by a man.

Scarlett McNally, a consultant orthopedic surgeon for 20 years, stated that there is “increasing evidence of a different experience for female surgeons, with many being put off surgery and reporting historical ‘microaggressions’.” Furthermore, female patients may feel more at ease talking to a female surgeon before the operation about steps they can take to improve their chances of a good outcome, such as quitting smoking to help ensure a bone graft takes, she added.