The number of foreign medical graduates from Muslim-majority countries coming to the United States to become doctors has declined by 15 percent under the Trump administration, exacerbating shortages in America's physician workforce, a study said on Monday.

International medical graduates represent about a quarter of practicing doctors in the United States.

They are required to take several licensing exams and then complete two or three years of training to practice medicine in the United States.

Overall, citizens from Muslim-majority nations made up 4.5 percent of the U.S. physician workforce in 2019, with Pakistan, Egypt and Iran historically providing the bulk.

The number of graduates from Islamic nations applying for certification in the United States rose from 2009-2015, peaking at 4,244, before falling steadily to 3,604 in 2018, a decline of 15 percent.

A small drop occurred in 2016, the year in which Trump was elected but his predecessor Barack Obama was still in office, before hastening in 2017 and 2018.

The study appeared in the Journal of the American Medical Association, and was led John Boulet, vice president of the Educational Commission for Foreign Medical Graduates that oversees the certification process.

Boulet and colleagues said that recent U.S. policies, such as the travel ban on Muslim-majority countries "affect the inflow of IMGs International Medical Graduates) by restricting travel to the country for citizens from specific nations."

They added: "Even a perceived immigration ban could affect who chooses to complete the requirements for... certification" while potential difficulty obtaining a visa could dissuade the program directors of medical residencies from making a job offer.

The U.S. demand for physicians has long outstripped supply for a variety of reasons, from population growth and aging, to a federal cap on funding for residency training.

As a result, the United States could see a shortage of as many as 122,000 doctors by the year 2032, according to a 2019 report by the Association of American Medical Colleges.

Some economists also argue that the short supply of doctors has led to a surge in their wages - costs that are eventually passed down to patients.

"To the extent that citizens from some countries no longer seek residency positions in the U.S., gaps in the physician workforce could widen," the authors said.

The attractiveness of the United States as a destination may have also waned in comparison to other countries like Canada, New Zealand, Australia and Britain, the authors wrote.