U.S. President Donald Trump's travel ban for citizens from seven Muslim-majority countries could end up impairing the health of Americans, according to a new study led by a Harvard University-based Japanese researcher.

In the study, published Friday in the BMJ (formerly known as British Medical Journal), researchers led by Yusuke Tsugawa — of the department of health policy and management at Harvard — found that patients treated by internal medicine doctors who graduated from international medical schools had a lower mortality rate than patients cared for by general internists who graduated from U.S. schools.

The team's study of some 1.2 million Medicare patients admitted to U.S. hospitals with general conditions from 2011 to 2014 showed that their chances of dying within 30 days of admission was 5 percent lower if they were treated by international graduates. The research covered 24,638 U.S.-trained doctors and 19,589 trained overseas.