Male doctors make about $12,000 a year more than female doctors, even after specialty, work hours and other factors are considered, U.S. researchers have found.

Investigators surveyed 800 physicians who received competitive federal research grants starting in 2000 and followed them until mid-career.

It was 'surprising and disturbing' to find men and women doing similar work in medicine are paid quite differently, Dr. Reshma Jagsi says. (Courtesy of University of Michigan)

Overall, without considering variable factors, the average annual salary was $200,422 for men and $167,669 for women, a difference of $32,764, the researchers said in Wednesday's issue of the Journal of the American Medical Association.

"To see that men and women doing similar work are paid quite differently in this cream-of-the-crop sample is both surprising and disturbing," the study's lead author Dr. Reshma Jagsi, an associate professor of radiology oncology at the University of Michigan Medical School, said in a release.

Over 30 years, the researchers estimated a woman would earn over $350,000 less than a similar male colleague by the end of their careers.

The researchers considered specialty, academic rank, leadership positions, publishing record and research time in their analysis of the 247 female and 553 male physicians, who were also asked about their marital status and children.

Findings included:

• Women tended to be in lower-paying specialties, with 34 per cent of women and 22 per cent of men in the lowest-paying category.
• Women were less likely to hold administrative leadership positions (10 per cent versus 16 per cent).
• Women had fewer published articles (average of 27 versus 33).
• Women worked fewer hours (average, 58 versus 63 hours).

Much of the overall gender difference was explained by specialty, the researcher said.

"It may be important to consider the gender gap without adjustment for specialty if women do not choose but rather are encouraged to occupy lower-paid specialties or if those specialties pay less partly because they are predominated by women," the study's authors wrote.

Senior author Dr. Peter Ubel, a professor at the Sanford School of Public Policy at Duke University in Durham, N.C., cautioned against attributing the salary difference to conscious discrimination.

"For all we know, women are paid less in part because they don't negotiate as assertively as men, or because their spouse's jobs make it harder for them to entertain competing job offers," Ubel said.

"Nevertheless, whatever the reason for the salary disparity, academic medical centres should work to pay more fairly. A person's salary should not depend upon whether they have a Y chromosome."

The Robert Wood Johnson Foundation, University of Michigan Office of the Vice President for Research, and U.S. National Institutes of Health funded the research.