David Phillips and Gwendolyn Barker believe there is a clear link between deadly medical errors and the arrival of new residents. They also examined hospitals without residency programs. They found no unusual increase in deaths caused by drug errors.

Medical residents may stay at a teaching hospital for three years or more. They are given responsibilities for patient care. But they are not supposed to work alone. They are supervised by more experienced doctors.

The researchers say teaching hospitals should examine the responsibilities of new doctors. They also say the new residents should be supervised more closely and should be taught more about medication safety.

The researchers say if hospitals do these things, they will reduce medication errors, as well as the costs related to these mistakes.

The findings are published in the Journal of General Internal Medicine.

And that's the VOA Special English Health Report. For more health news, go to voaspecialenglish.com. You can read and listen to all of our reports and write comments. You can also write to us on Facebook and Twitter at VOA Learning English. I'm Jim Tedder.