“There are inequalities in a lot of different contexts, but when someone is suffering from a heart attack, you might expect that there would be no gender differences because every physician will go in trying to save their patient’s life,” says Huang, a professor of organizational psychology at Harvard Business School. “But even here, we see a glass ceiling on life.”

Overall, the team found that female physicians outperformed their male colleagues, and their patients were, on the whole, more likely to live. That’s consistent with other studies: For example, it’s what Ashish Jha from the Harvard T. H. Chan School of Public Health found in 2016, in a study of almost 1.6 million U.S. patients. “If male physicians had the same outcomes as female physicians, we’d have 32,000 fewer deaths in the Medicare population,” Jha wrote. “That’s about how many people die in motor vehicle accidents every year.” It was a striking finding, especially since women doctors still earn $105,000 a year less than their male peers.

Huang and her colleagues also found that women with heart attacks are, on the whole, less likely to survive than men. Again, that fits with earlier studies, and with what Healy wrote about in 1991. Heart attacks look different in women than in men: Rather than the classic gripping chest pains, they can also be presaged by indigestion, or discomfort in the arms, neck, jaw, stomach, and back. Decades of sex-biased research means that these symptoms are seen as “atypical.” As such, women delay seeking help for them. And when they do seek help, they’re often dismissed and less likely to be offered diagnostic tests.

But “the penalty for being female is greater” when women are treated by male physicians, says Greenwood. He and his colleagues found that there’s no gender gap in survival when the doctor is female. Women patients only fare worse than men when their doctor is male.

To put some numbers on these differences, the survival rate for men treated by female doctors is 88.1 percent, compared with 86.6 percent for women treated by male doctors—a reduction of 1.5 percentage points. These differences persisted even after the team accounted for factors like the doctors’ years of experience and the patients’ age, ethnicity, other diseases, educational level, or the hospitals to which they were admitted.

Greenwood and Huang doubt that these differences are driven by explicit sexism. Instead, it might be that women are more comfortable explaining their symptoms to female doctors, who are in turn more likely to connect those symptoms with heart attacks. It could also be, as the team writes, “that the most skillful physicians—i.e., female physicians—provide the highest return to their skills when treating the most challenging patients—i.e., female patients.”

But Ashish Jha says that “the data are less clear than [the team] makes it out to be.” While it’s clear that male physicians are better at taking care of men with heart attacks than women, “it’s harder to tell if female physicians have no such gender disparity because their numbers are so small.” (In the U.S., there are only half as many female doctors as male ones.)