Working long hours is considered a hallmark of a medical residency. But in recent years, concerns have risen about how shifts that can last days affect a doctor’s ability to function.

The results of a new study quantify the negative effects and show that the performance of fatigued residents is comparable to how they would act after imbibing three or four cocktails.

An 80-hour limit for a resident’s workweek was introduced in July 2003 in response to concerns about overwork. In the new study, J. Todd Arnedt of the University of Michigan and his colleagues measured the performance of 34 doctors, who had been on call, on an attention test and in a driving simulator. The volunteers took part in the tests on four different occasions, after working mostly day shifts with only a few overnight calls, or after working intense overnight shifts that added up to about 80 hours in a week. For some of the tests, the doctors were also given alcoholic drinks or nonalcoholic placebos. After a month of difficult work schedules, the doctors exhibited reaction times that were seven percent slower than their responses after working a lighter schedule. In the driving simulator, doctors coming off a month of working nights displayed comparable skills to the subjects who had an easier schedule but had a blood-alcohol level just below the legal driving limit. What is more, the post-call doctors were 30 percent more likely to not maintain a steady speed in the driving simulator compared to well-rested doctors who had been drinking.

More here.