To get the fairest comparison, the study authors took into account work hours, academic titles, medical specialties, age and other factors that influence salaries. They included only doctors who were involved in research at U.S. medical schools and teaching hospitals, all at the same stage in their careers. And they still found men's average yearly salaries were at least $12,000 higher than women's.
Over a 30-year career, that adds up to more than $350,000.
The results are sobering and "disappointing. I think we have much work to do," said lead author Dr. Reshma Jagsi, a breast cancer radiation specialist and researcher at the University of Michigan.
Why the big disparity?
Two women who have been prominent in medical research say this: Men tend to be more aggressive at self-promoting and asking for pay raises than women.
"Male faculty members are willing to negotiate more aggressively. It may be social and cultural. It seems to be fairly deep-rooted," said Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital and a professor at Harvard Medical School.
Manson, who as a division chief helps makes salary decisions, says men much more frequently than women ask her for salary increases and promotions.
Dr. Julie Gerberding, former head of the federal Centers for Disease Control and Prevention, agrees.
Gerberding did infectious disease research at the University of California at San Francisco before joining the CDC and says early in her career she was bothered that relatively few women held high-paying leadership positions in academic medicine.
"There were some moments when I was angry, but that was motivating. I thought it was an intolerable situation and it just motivated me to work harder," said Gerberding, who left CDC in 2009 and now heads Merck & Co.'s vaccine unit.
She and Manson declined to say if they think they've been paid less than male counterparts.
While previous studies have found that female doctors are frequently paid less than male doctors, many observers have assumed that's often related to having children - working fewer hours, or choosing less time-consuming, lower-paying specialties to allow time for child-rearing.
The new study did find more women in less lucrative specialties, including pediatrics and family medicine, and more men in the highest-paying fields, including heart surgery and radiology. But it still found salary inequities even among women and men without parental responsibilities, in similar jobs.
The findings are from a mailed 2009-10 survey of 800 doctors who had received prestigious federal research grants in 2000-03. The findings appear in Wednesday's Journal of the American Medical Association.
Women's yearly salaries averaged almost $168,000, compared with $200,400 for men - a difference of more than $32,000. Taking into account academic rank, choice of medical specialties and other factors that could affect salary, the difference wound up being $12,194.
Dr. Peter Ubel, the study's senior author and a Duke University professor, said there's no formula for pay increases; doctor-researchers don't automatically get a raise every time one of their studies is published. That makes the decision-making process more subjective, he said.
About equal numbers of men and women attend and graduate from medical school. But women make up a tiny portion of leadership positions at medical schools. And Jagsi said people in hiring positions may be biased, perhaps unconsciously, toward hiring men.
Ann Bonham, chief scientific officer at the American Association of Medical Colleges, a national group that represents U.S. medical schools and teaching hospitals, said medicine isn't the only field with gender differences in salaries. Medical schools are aware of the problem and are moving to ensure that decision-making on salaries "is a fair process and transparent. Nobody intends to be unfair in distributing resources," Bonham said.
Gerberding praised the study for raising awareness.
"Institutions need to take this information seriously and take a hard and closer look at their own salary parity issues," she said. Career advancement often depends on having a strong mentor and sponsor, so women and men in leadership positions at medical schools and teaching hospitals should make sure they're actively advocating for qualified women and suggesting them for promotions, Gerberding said.