Most Americans pay little attention to their chronic sleep deficits -- until there's a tragedy.
Lack of sleep is a safety concern that's gotten some attention recently, whether it's airline pilots, truckers, medical residents or even just everyday people driving drowsy.
Earlier this month, unions representing pilots and air traffic controllers said that lack of sleep was probably a factor in the crash of Comair Flight 5191, which took off from the wrong runway in predawn darkness at Lexington, Ky.'s Blue Grass Airport. The captain, co-pilot and air traffic controller all had had an inadequate amount of sleep leading up to the Aug. 27 crash, according to a study commissioned by the Air Line Pilots Association.
"It happens on a daily basis," said Fred Turek, director of the Center for Sleep & Circadian Biology at Northwestern University. "It only makes the news if there's a major loss of life."
Circadian rhythms govern our body's natural sleep-wake cycles. It's why we feel sleepy at night -- especially during the hours between 4 a.m. and 6 a.m. -- and it makes it difficult to sleep during most daylight hours, unless you're sleep-deprived.
"They are such a part of everyday life that we take it for granted," Mr. Turek said of sleep-wake cycles. "What people don't recognize are the consequences. All it takes is for you to close your eyes for a microsecond." Mr. Turek said most people realize they are alert at certain times of the day, sleepy at others.
The Comair crash brought sleep deprivation to the front page, but past research has frequently found safety issues for pilots when sleep is limited.
A 2003 article in the Journal of Safety Research included an FAA analysis that found an increased probability of airline accidents as duty time increased for pilots. The article, by FAA economist Jeffrey Goode, said that most scientists think pilots need eight hours of sleep in a rest period and current regulations don't ensure this. According to federal rules, pilots can fly for only eight out of every 24 hours, but that doesn't include "duty" time, which includes standby time and time used for pre-flight preparations.
Mr. Turek said that while the major airlines have built in enough rest hours for pilots, they can't enforce how pilots use them. "There's 12 hours between flights, but they may only spend a few of them on sleeping," he said.
In the early days after the Comair crash, sleep groups, such as the American Academy of Sleep Medicine, issued statements of concern about sleep deprivation, particularly related to the air traffic controller on duty, who had only about two hours of sleep in the day before the early-morning crash. The plane took off just after 6 a.m.
And it's not just airline pilots who are sometimes sleepy behind the wheel.
The National Highway Traffic Safety Administration estimates that more than 100,000 vehicle crashes each year are due to drowsy drivers, and studies have found that people who are sleep-deprived are as dangerous behind the wheel as those who are legally drunk. About 1,550 people each year die in car crashes related to drowsy driving.
Research has found that circadian biology also affects vehicle crashes; wrecks linked to drowsiness are common late at night or in the early morning hours. There's also another circadian dip in the mid-afternoon, with a spike in related accidents. In 2003, New Jersey became the first state to enact a tough law against drowsy driving -- sleep-deprived people who cause fatal accidents can be jailed for up to 10 years.
Mr. Turek said being a sleep specialist who is up on circadian rhythms has altered his patterns. He never drives between 11 p.m. and 6 a.m. He's worried not only that he might fall asleep at the wheel, but that other drivers on the road could as well. However, Mr. Turek said he believes the risk of an airline crash is so remote that he doesn't avoid flying in the early morning or late at night.
Kathryn Hansen, director of the Sleep Wellness Center at St. Joseph Hospital, said that most people don't value sleep as much as they should.
"Sleep has often been underrated in our society," she said, adding that many Americans are so chronically sleep-deprived that they don't have any idea what normal functioning and rest patterns feel like. Sleep deprivation is cumulative, meaning that adults who don't get the recommended seven to eight hours a night build a "sleep debt." That can't be repaid in any way but sleeping more, say during a vacation, or by devoting more daily hours to sleep.
But millions of people -- especially night workers and people who switch shifts on a regular basis, such as pilots -- are so far behind that they can't catch up. The American Academy of Sleep Medicine estimates that about 20 million Americans work rotating shifts that put them at risk for sleep-deprivation-related accidents and illnesses.
Ms. Hansen said sleep deprivation also is linked to a host of health problems that can shorten one's life span -- not just in accidents. Sleep deprivation is linked to high blood pressure, depression, weight gain, increased blood sugar levels and lowered immune function, among other problems.
Mr. Turek said that while people want to believe that they can function well on less than seven or eight hours of sleep, research shows otherwise. "There's no substitute for sleep," he said.
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