|
||||||||
|
MEDICINE Lost Memories--A Side Effect of Education?Chronic stress and lack of sleep go with the territory of being a medical trainee. Yet new research in the neurosciences shows that the habit of working too much and sleeping too little has brain-altering effects that may prevent medical students, interns, and residents from accomplishing their most important task, learning.
"The intern typically wakes up and begins a 36-hour vigil," said Charles Czeisler. He and other conference participants described how lack of sleep and other forms of stress can interfere with medical education. (Photo by Steve Gilbert) The new research was the subject of an afternoon symposium, "How the Brain Learns: Implications for Medical Education from the Neurosciences and Cognitive Theory," held on Sept. 23 and sponsored by the Academy at HMS. Daniel Lowenstein, who co-organized the event with Antoinette Peters, opened the program by commenting that the findings have been presented in other settings at HMS but never before with an eye to better understanding the current state of medical education. "For the Medical School itself, I do not think we have had an experience like this," said Lowenstein, dean for medical education at HMS and the Carl W. Walter professor of neurology and medical education. Peters is an HMS assistant professor of ambulatory care and prevention. The unique focus yielded some provocative insights as participants discussed the effects of the medical school lifestyle, in particular chronic stress and sleep deprivation, on aspects of the brain, such as its ability to make new neurons. Do Adult Brains Make Neurons?One of the central tenets of modern neuroscience has been the idea that mammals are born with all their neurons. That dogma was called into question several years ago when Elizabeth Gould, now at Princeton University, and colleagues found new neurons in the brains of adult rats and other mammals. Gould, the first speaker, has since found that stress--defined as stimuli that activate the hypothalamus-adrenal-pituitary axis--can impair this neuron-making ability, not just in stressed adults but in their offspring.Even nonstressed laboratory animals appear to make fewer neurons than animals raised in more naturalistic settings, Gould said, suggesting that the ability to make new neurons is affected by a variety of factors, including sensory and social deprivation. Gould did not comment directly on the implications for stressed-out medical trainees. That was the job of the next speaker, Charles Czeisler, whose subject was a different kind of deprivation, namely of sleep. He painted in discomfiting detail the grueling schedule of the average medical trainee and its often dangerous consequences. "Currently, interns and residents work up to 140 hours a week," said Czeisler, HMS professor of medicine at Brigham and Women's Hospital. "There are only 168 hours in the week." Commuting, eating, showering--in addition to sleep--must be taken out of the remaining 24 to 28 hours, he said. To squeeze in all those hours, trainees work 36 hours shifts, many of which begin at 4 a.m., when the body's internal, or circadian, clock is normally promoting sleep. Add to that the typical decline in alertness after 16 hours of being awake, Czeisler said, and it is no wonder that medical students enter a "zone of vulnerability." He cited studies of truck drivers to show how the risk of making mistakes explodes from beginning work too early and working too many consecutive hours. For example, the relative risk of a fatigue-related crash increases 15-fold after 13 hours on the road and 56-fold after a 20-hour drive. The last accident rate equals that of people with a blood alcohol level of 0.1 percent. Interns and residents, especially those who are on call, are often asked to perform cognitive and motor skills more demanding than driving. And they often do so very shortly after waking. Yet studies show that the transition from sleep to wakefulness often requires the better part of an hour. "The brain does not go from 0 to 70 in 60 seconds," Czeisler said. He and colleagues are embarking on a new project to assess the effect of this schedule on patient safety and medical errors. Five physicians will be appointed to shadow two groups of interns, one following the Association of American Medical Colleges' recommendation of no more than 12 continuous hours of duty, the other following the standard one-in-three days of on-call duty. Disordered SleepingSleep deprivation is extreme in interns and residents, but medical students practice their own version. "Harvard students participate in what I call sleep bulimia," said Robert Stickgold, HMS assistant professor of psychiatry. This tendency to cut back on sleep during the week and to make up for it on the weekends interferes with their ability to learn--the raison d'etre of a student. Stickgold and his colleagues have shown that not sleeping the night after learning a new task, or even sleeping less than the ideal eight hours, greatly impairs learning (see Focus Dec. 1, 2000). It does so, at least in part, by depriving the brain of REM, or dream, sleep, which appears to play a critical role in forming new memories.Other experiments by Stickgold's group suggest that rather than literally replay the day's events, dreams arrange those events in new contexts, producing meaningful associations with previously held information (see Focus Oct. 27, 2000). "REM sleep appears to take information from our daily lives and integrate it into a larger semantic network," said Stickgold. Meaning is something our waking brains seek out too, said Daniel Schacter, Harvard University professor of psychology. In experiments, meaningful words were better remembered. Schacter and colleagues also found that such words often triggered special brain regions. As important as meaning may be, emotions may be more important, said Daniel Tosteson, the Caroline Shields Walker distinguished professor of cell biology, during the discussion after the presentations. "It has long struck me that the most important determinants of learning are not cognitive but affective," he said. --Misia Landau |
