Dr. West and colleagues surveyed 356 residents at 163 medical schools globally. They found that 39% reported making at least one major medical error during the study period, and these doctors were also more likely to say they were sleepy, fatigued, or stressed. “ What we have shown in this data is that fatigue is important, but it’s only part of the issue and previous studies have not paid much attention to the distress factors,” Dr. West said. “ Over the course of their training and the course of their career everyone has made a major error. Everyone tries to be perfect but no one is.” He said only limiting work hours may not be enough.