NPR explains both sides of the controversy behind a study that seeks to find out which schedule for medical residents—one that allows for no more than 16 hours without a break but may result in more night shifts or a more flexible schedule that could allow the young doctors to work up to 30 hours—is safest and teaches residents the best.

“If we want to take the best care of patients now and in the future, we really need to understand much more about the intricate balance of hours, education and care,” says David Asch, a professor of medicine at the University of Pennsylvania, who is leading the study.

But this study and a similar project have triggered objections from Public Citizen’s Health Research Group, an advocacy organization based in Washington, D.C., and the American Medical Student Association, which represents medical students.

The groups argue the studies put patients and residents at risk.

Sleep-deprived residents are more likely to injure themselves while doing procedures such as drawing blood, inserting intravenous lines or suturing wounds, says Michael Carome, who heads the health research group. The accidents could lead to infections with viruses such as hepatitis and HIV, he says. And tired residents tend to get into more car accidents after work.