(Reuters Health) - In internal medicine, women earn less than men even when they’re in the same specialty and working the same hours in similar types of medical practices, a U.S. study suggests.

Overall, half of male internists have annual salaries of at least $250,000, compared with $200,000 for female internists, the analysis of survey data from 374 full-time physicians found. That translates into women earning 80 cents for every dollar earned by men, researchers report in the Annals of Internal Medicine.

“Compensation in medicine is extremely complex and often opaque,” said study co-author Renee Butkus, director of health policy at the American College of Physicians in Washington, D.C.

Total compensation can include base salaries, stipends for other positions, various productivity standards, clinical and nonclinical support, and office and laboratory space, Butkus said by email. Still, it can be hard for women in medicine to figure out whether, or why, they’re earning less than men.

“Women in medicine face other challenges, including a lack of mentors, discrimination, gender bias, cultural environment of the workplace, imposter syndrome, and the need for better work–life integration,” Butkus added. “These all have an impact on career advancement and compensation, and a concerted effort must be made to address all of these things to realize the full potential of women in medicine.”

For the survey, researchers asked what physicians for their estimated annual income before taxes, including any salary, bonus, and profit-sharing contributions. For physicians who owned businesses, researchers asked about earnings after tax-deductible business expenses but before income tax.

Women earned less than men in every internal medicine specialty, ranging from a gap of $29,000 for internal medicine specialists to a gap of $45,000 for sub-specialists.

Among physicians who owned practices, women typically earned $72,500 less than men each year.

When women were employees rather than business owners, they generally earned $43,000 a year less than men.

For doctors who spent most of their time providing direct patient care, women’s annual income lagged what men made by about $37,500.

When doctors had management or administrative roles, women earned about $52,500 a year less than men.

Gender differences in salary were the same regardless of whether doctors had children.

One limitation of the study is that only about 56 percent of physicians invited to participate in the survey did so.

All of the survey participants were members of the American College of Physicians, and it’s also possible their responses don’t reflect income of internists who weren’t members or of physicians in other medical specialties.

“This descriptive study does not try to fully adjust for potential factors that might contribute to these disparities but still it shows that women and men in very similar fields - doing research or teaching young physicians - have huge differences in their salaries,” said Dr. Barbara Turner of the Keck School of Medicine at the University of Southern California in Los Angeles.

“It matters to patients because pay inequities lead to distrust of the employer, a loss of morale, feeling undervalued, and may lead women just to drop out of the field,” Turner, co-author of an accompanying editorial, said by email. “However, we desperately need them in areas that men do not deign to enter such as primary care and teaching roles plus women are half of the trainees in medical schools, so it is in the public’s interest to be sure that they are careers are rewarding and sustained.”

SOURCE: bit.ly/2wYH0qu Annals of Internal Medicine, online August 6, 2018.