Too few women and minorities are entering certain medical specialties in the U.S., researchers say.

Diversifying the physician workforce may be key to addressing health disparities and inequities, Dr. Curtiland Deville of Johns Hopkins University in Baltimore, Maryland, who worked on the study, said in an email.

"Minority physicians continue to provide the majority of care for underserved and non-English speaking populations,” Dr. Deville added.

Yet "in no specialties . . . were the percentages of black or Hispanic trainees comparable with the representation of these groups in the US population," he and his colleagues wrote in JAMA Internal Medicine.

Medical schools have been trying to increase the diversity of their students, "with perhaps the assumption that this increased diversity will translate downstream to all specialties," Dr. Deville told Reuters Health.

But, he added, his team's new study shows that in some specialties, such as radiology, orthopedics, and otolaryngology, there's still "disproportionate underrepresentation of women and minorities.”

Using publicly reported data, the researchers determined that of the 16,835 medical school graduates in 2012, 48 percent were women and 15 percent were minority groups (including 7 percent Hispanic and 7 percent black).

Also in 2012, there were 115,111 trainees in "postgraduate" medical education - for example, in internships and residencies - of whom 46 percent were women and 14 percent were minorities (8 percent Hispanic and 6 percent black).

Of the 688,468 practicing physicians in 2012, 30 percent were women and 9 percent were members of underrepresented minorities, including 5 percent who were Hispanic and 4 percent who were black.

In 2012, women accounted for 82 percent of trainees in obstetrics and gynecology and for 75 percent of pediatrics trainees. Women also accounted for more than half of all trainees in dermatology, family medicine, pathology, and psychiatry - but for only 14 percent of trainees in orthopedics.

Among black trainees, family medicine and obstetrics and gynecology were top picks, while otolaryngology (ear, nose and throat) was least favorite. Among Hispanic trainees, top picks were psychiatry, family medicine, obstetrics and gynecology and pediatrics, while ophthalmology was least favorite.

Representation was increased in certain specialties for females, Blacks, and Hispanics but remained largely unchanged in others, Dr. Deville told Reuters Health.

What's needed to increase diversity in medical specialties?

“First is the need to increase the available pipeline of diverse medical students,” Dr. Deville said. “This is especially the case for Blacks, Hispanics, and other underrepresented groups. In parallel, is the need to ensure that female, black, and Hispanic medical students are exposed, prepared, and engaged to join all medical specialties."

In an interview with Reuters Health, Marc Nivet, chief diversity officer at the Association of American Medical Colleges, said this is “an important paper primarily because, in my mind, it calls to question if we need to be doing more research to figure out why women remain predominantly in three specialties, family medicine, pediatrics and OBGYN. Is that based on choice or are they in some way being relegated to those particular fields, or not being given advice to go into orthopedics or surgery specialties. Is there gender bias at play?”

He added, “I do think there is a role for hospitals and medical schools to make sure that their environments are as inclusive as possible. A minority or a woman shouldn't look at a particular field like orthopedics and say, 'Well, that's not for me.' There should be training that's happening for the graduate medical education leaders (and) for the faculty members of institutions to make sure that they are exposing all students to different opportunities so they can make the right choice for themselves.”