The results of a study published this month in the American Journal of Surgery will certainly strike some of us as counterintuitive. The researchers looked at the effect of sleep deprivation on surgical residents and found that sleepiness does not affect performance of a previously learned task. For patients at Portland hospitals, the broad implication is that the surgeon with just two hours of sleep is no more likely to make a mistake than the well-rested surgeon.

The study did not involve surgery on patients. Rather, the medical students used a simulator. On the first day, they practiced for about 45 minutes on all three levels of a particular task. They all got a good night’s sleep and came back on the second day. They performed the same tasks to get a baseline score. The researchers tossed in another task during the test to determine how well the subjects dealt with unexpected events.

That night, half of the students got another good night’s sleep while the other half slept for just two hours. On the third day, they all took the same test. They also learned a different task and were tested on that; the researchers wanted to find out if lack of sleep would have any effect on learning something new.

Surprisingly, the sleep-deprived subjects performed as well as the well-rested. The only difference was how hard their brains had to work: For the sleep-deprived, the same test results took more effort. This “cognitive workload” has been the subject of other studies.

One of the most disconcerting things to see as you are wheeled into surgery is your surgeon yawning. The worry is not that the surgeon will fall asleep during the procedure; it is that the surgeon is not at his or her best. We assume that a sleepy surgeon is more likely to make a mistake, like wrong-site surgery or nicking an artery, but, according to a study in the American Journal of Surgery, that is not actually the case.

The study involved training medical students on specific tasks. Half of the group then got a full night’s sleep, while the other half got just two hours of sleep. When they repeated the tasks, the results were the same: The sleep-deprived students performed the tasks as well as they had the day before. They also were able to learn a new task just as well as they had when fully rested.

What was different, though, was the cognitive workload of the sleep-deprived group. Using a tool developed by NASA, the researchers were able to measure how difficult a task was for the study participants. They found that the sleep-deprived group had to work harder to accomplish the tasks.

At first glance, this isn’t a surprise. Of course our brains work harder when we don’t get enough sleep. The surprise is that the outcome was the same: Sleep deprivation increased the cognitive workloads and the students performed tasks they knew and learned new tasks just as successfully as they had with a full night’s sleep.

Other studies say this shouldn’t be the case. If the brain is stressed, performance suffers: There is a greater risk that a surgeon will make a mistake, especially if something unexpected occurs during surgery.

The results are not reason to toss out all the existing studies, though. The researchers recommend more work in the area of cognitive workload and sleep deprivation.

Source: Penn State Hershey, “Sleepiness may affect surgeons’ ability to deal with the unexpected,” May 2012