Lack of Sleep Causes Fatigue, Impaired Reaction Times

From the WebMD Archives

Sept. 30, 1999 (Atlanta) -- People with mild to moderate sleep apnea have at least as poor reaction times as people too drunk to drive, according to a recent study. The findings affect those behind the wheel and others who engage in hazardous activities while fatigued.

Lead investigator Nelson B. Powell, MD, describes the findings as "somewhat surprising." He says, "We had thought that it would be the severe patient with obstructive sleep apnea who would be the one that we would have to worry about." Powell is clinical professor of psychiatry at Stanford University.

People with mild to moderate sleep apnea stop breathing several times an hour during sleep and wake up repeatedly. Because many people with sleep apnea wake up without their knowledge of doing so, the problem often goes undiagnosed. This leads to daytime drowsiness, decreased ability to function during the day, and decreased quality of life. Among adults aged 30-60 years in the U.S., 2% of all women and 4% of all men have this disorder. Although the disorder is more common in overweight people, sleep apnea can occur in anyone.

This study examined reaction times of 80 healthy, light to moderate drinkers with no history of snoring, sleep disorders, or drug and alcohol abuse. They compared them to 113 patients with documented, mild to moderate sleep apnea, and to 11 healthy, nonsnoring subjects who did not drink alcohol or have sleep apnea. All subjects received a simple reaction time test. They pressed a button as quickly as possible each time after a bright red light was displayed.

In the first test, subjects with sleep apnea performed worse in every category than did subjects with an average blood alcohol level that was approximately 1.5 times the legal limit for operating a commercial vehicle in California. In the second and third trials, subjects in the sleep apnea group again did as poorly or worse than those whom had been drinking.

Different people handle sleep deprivation differently, according to Powell. "It all depends on whether they have had alcohol, sedative medications, how much stress they're under, and how much sleep deprivation it is," he says. "Some people need 4 hours a night and others need 12 hours a night. ... You can deprive someone of an hour to an hour and a half a night of their normal sleep, and by the end of the week you can have accumulative sleep debt that will make that person so sleepy that they can't function."

Most people know when they haven't had enough sleep, says Powell. "They're tired," he says. "They wake up in the morning and 1/4 their body just doesn't feel right. They may have a headache or feel a little nauseated. [On the other hand,] a lot of people are such hard-chargers that they work through it." He adds that the findings have relevance to people who stay up all night once in a while and to people who work a swing shift and regularly fail to get a decent night's sleep.

"Be as responsible as you would if you were drinking alcohol," Powell says. "Most people know now that if they've had a couple drinks they are not going to get into a car and drive home.