"People don't respect sleep enough," says Daniel O'Hearn, a sleep disorders specialist at Johns Hopkins University. "They feel they can do more--have more time for work and family--by allowing themselves less time for sleep. But they do sleep; they sleep at work, or driving to work."
Nodding off at work isn't just unproductive; in the worst cases, it can cause serious industrial accidents. The 1989 Exxon Valdez Alaskan oil spill, for example, was reportedly due at least in part to the severe fatigue of the tanker's sleep-deprived third mate.
Also, like drunk driving, drowsy driving can kill. The National Highway Traffic Safety Administration estimates that more than 200,000 crashes each year involve drivers falling asleep at the wheel, and that thousands of Americans die in such accidents annually.
"Besides being an unpleasant sensation, when we're tired, we're less alert and less able to respond reflexively," says FDA drug reviewer Bob Rappaport, M.D.
Lack of sleep can cause memory and mood problems, too, Rappaport says, and may affect immune function, which could lead to an increased incidence of infection and other illnesses. In studies performed on rats, prolonged sleep deprivation resulted in death.
Beyond the observable consequences of sleep deprivation, why humans--or any animals, for that matter--need sleep remains largely a mystery. "What happens in the brain while we're sleeping is what we're trying to untangle," says James Kiley, director of the National Center for Sleep Disorders Research of the National Institutes of Health. "We're just beginning to understand why a third of our life is spent sleeping. What we do know is that sleep is an important biological need, like food and drink, and that the brain is very active while we're sleeping."
The leading sleep theories focus on "rest and resuscitation for the body and the psyche," says Rappaport. During sleep, the brain may recharge its energy stores and shift the day's information that has been stored in temporary memory to regions of the brain associated with long-term memory.
So just how much nightly R and R does a person need? That can change throughout one's life based on age and other factors affecting the internal clock or "circadian rhythms." For most people, though, seven and a half to eight and a half hours of sleep each night fulfills the basic physical need, Rappaport says, adding that this is "very individual" and can range from as few as four or five hours to as many as nine or 10.
The Mayo Clinic in Rochester, Minn., defines an adequate amount of sleep as whatever produces daytime alertness and a feeling of well-being. People should not need an alarm clock to wake them if they are getting enough sleep, the Mayo Clinic says, while acknowledging that throwing away one's alarm clock may be unrealistic.
--T.N.
FDA Consumer magazine (July-August 1998)