SCIENCE OF SLUMBER | DYING TO SLEEP Dying to sleep Getting too little sleep can impair body and brain, and could even be deadly By Tina Hesman Saey or many people, days just don’t night may cause long-term — maybe even a driving simulator with electrodes taped seem long enough. In order to permanent — changes in the brain, some to her head. She pushes the accelerator so F cram everything into one 24-hour of which may predispose people to men- that her virtual car buzzes along at just period, something has to give. Judging by tal disorders such as depression. over 60 miles per hour on a dark road many surveys of Americans, it’s sleep. Just one night of short sleep has been illuminated only by her headlights. White Sleep is regarded by some as unpro- shown to increase levels of inflammatory poles flash by. Suddenly, around a bend, ductive, wasteful downtime. People who chemicals in the blood (SN: 10/11/08, the back of a large cargo truck looms in the would rather hit the hay than the dance p. 14) and increase hunger-promoting darkness. Heather quickly brakes to avoid floor are told that only losers snooze and hormones. A week of getting just two colliding with the slow-moving truck. that they can sleep when they’re dead. hours less sleep per night than usual But new data about sleep’s benefits changed the way people in one study Drowsy driving More than one-third of U.S. suggest that losing sleep might speed responded to glucose, mirroring a change drivers have fallen asleep behind the wheel. While most of those surveyed were startled up death’s arrival. Recent research also seen in people who develop diabetes. awake, some crashed. shows that people who don’t snooze And lack of sleep can also have immedi- Percentage of people who have nodded off enough face a higher risk of losing their ate injurious or fatal consequences: The while driving, by age health than those who regularly get a National Highway Transportation Safety 37% 40% 41% 42% good night’s sleep. Administration estimates that drowsy- 30% “What is certain is that we can’t do driving crashes result in about 40,000 18% without sleep,” says Peter Meerlo, a nonfatal injuries and 1,550 deaths each neuroscientist at the University of year, probably a conservative estimate. Total 16–20 21–29 30–45 46–64 65+ Groningen in the Netherlands. Now, scientists are trying to understand Some of the consequences of lost sleep not only how sleep deprivation affects Hours slept the night before driving drowsy are immediate, obvious and unpleasant, driving performance, but also why one ≤ 4 hrs such as a toddler’s crabbiness after miss- sleepy person might drive fine while ing a nap. Older children and adults get another becomes a road menace. 24% ≥ 8 hrs 17% irritable when tired, too. Sleepy students 5 hrs 16% don’t learn or perform as well as their Too tired to function 17% well-rested peers (SN: 09/09/06, p. 174). Nodding off behind the wheel is a com- 26% 7 hrs And nodding off at work probably won’t mon occurrence in David Dinges’ lab at 6 hrs help anyone get a promotion. the University of Pennsylvania School of Other penalties for staying up too late Medicine in Philadelphia. Outcome of nodding off while driving can be far more serious, even deadly. Dinges and his colleagues limit volun- Studies have linked chronic sleep loss to teers’ time in bed to four hours a night for Ran off the road 10% obesity (SN: 11/17/07, p. 318; SN: 4/1/06, five nights, then let the volunteers sleep Crossed centerline 19% p. 195), heart disease, high blood pressure, up to 10 hours for two days. The aim of Wandered out of lane 33% diabetes (SN: 1/3/09, p. 5; SN: 1/19/08, the experiments is to learn more about Got in a crash 2% p. 46) and shorter lives (SN: 2/8/03, how the brain responds to the kind of Was honked at 6% p. 85) in people and laboratory animals. chronic sleep deprivation people expe- And now, a new study links sleep loss rience in real life, and to find out how Startled awake 92% in mice to Alzheimer’s disease plaques much sleep is needed to repay the debt. Other 9% (SN: 10/24/09, p. 11). And some evidence In the dimly lit laboratory, a volunteer SOURCE: 2002 SURVEY OF DISTRACTED AND DROWSY DRIVING/ suggests that stinting on sleep night after named Heather sits behind the wheel of NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION TOMMY LEONARDI PAGE: FACING 28 | SCIENCE NEWS | October 24, 2009 www.sciencenews.org Sleepy volunteers put pedal to the metal in a University of Pennsylvania driving simulator. Lab technician Christopher Jones demon- strates: electrodes on his head register brain waves on an EEG and the simulator measures his driving performance. SCIENCE OF SLUMBER | DYING TO SLEEP For each of the past four nights, Heather crashes and near-crashes recorded in a willingly deprive themselves of sleep, has gotten just four hours of sleep. “My study by researchers at Virginia Tech in says Eve Van Cauter, a sleep researcher limbs feel heavy,” she reports. She isn’t Blacksburg. The team fitted 100 cars with at the University of Chicago. “You can- used to this curtailed sleep schedule. cameras and sensors and then recorded not put a rat in front of the television, “I never stay up all night,” she says. “I drivers’ actions for about a year. A drowsy give him the remote and tell him, ‘you always get my sleep.” She is forgoing driver was four to six times more likely to have to stay awake,’ ” she says. shut-eye for a study of genetic differ- have a crash or near-crash. In contrast, People think that they are just too busy ences that may affect people’s responses reading, putting on makeup and dialing to bother with sleep. “We are ignoring that to sleep deprivation. a cell phone increased crash risks three- sleep, like exercise and proper feeding, is The electrodes on Heather’s head fold, the researchers found. crucial for health,” Van Cauter says. are monitoring her brain waves and No one could have predicted Heath- Those respondents who slept less than eye movements so that researchers er’s and James’ individual responses to six hours a night were also less likely than can detect even brief bouts of sleep. sleep deprivation, Dinges says. In his people who slept eight hours or more to But despite feeling tired, “a little light- studies, he has found that some people say that they work well and efficiently, headed and dizzy,” Heather hasn’t nod- fall apart after missing just a few hours eat healthy diets, engage in leisure activi- ded off when she’s not supposed to, and of sleep. Others, like James, show a slow, ties, exercise or have sex. Short-sleepers her performance on the driving simula- steady decline in their ability to remain also were more likely to smoke, drink tor and other tests hasn’t deteriorated vigilant and sharp on tests as their sleep caffeinated beverages and eat high-sugar from her well-rested showing. is cut short over the course of five days. or high-carbohydrate foods. The tests in Dinges’ lab have shown Then there are the people Dinges refers An analysis of several population just how severely most people’s perfor- to as “type 1s,” like Heather. Those peo- studies worldwide showed that children mance of daily activities can deteriorate ple’s performance on a variety of atten- who sleep less than 10 hours a night are with sleep loss. But Heather may be one tion and response-time tests doesn’t nearly twice as likely to be obese com- of a few rare people whose brains don’t change with five days of restricted pared with children who slept more than become mush when deprived of sleep. By sleep. “People are walking around with 10 hours. The study, published last year figuring out which genes keep Heather’s grossly different brain activity profiles,” in Sleep, also showed that short-sleeping brain functioning despite so little sleep, Dinges says. adults (those who got less than five hours researchers may be able to develop drugs of sleep per night) were more likely to be that affect those genes and help ordinary How much is enough obese, with body mass index increasing people resist making sleepy mistakes. No magic number exists for the amount with each hour of lost sleep. James, an architecture student, rou- of sleep people need each night. The Some data suggest that people who tinely pulls all-nighters, especially at the “normal” range includes as little as six sleep far more than average are also at end of a semester. He expected to feel hours (SN: 9/12/09, p. 11) and as much risk for health problems. Both short- and horrible after missing out on four hours as 10 hours of sleep per night, depend- long-sleepers were more likely to have of sleep each night for several days. “I ing on the person. But studies of various symptoms of “the metabolic syndrome,” thought I was going to be like a zombie, diseases show that sleeping about seven a cluster of conditions — including high not able to process things and short- to eight hours each night carries the least blood pressure, high cholesterol levels tempered,” he says.