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Friday June 15 5:41 PM ET

Overnight Sleep Loss Boosts 'Sleep Hormone'

By Alan Mozes

NEW YORK (Reuters Health) -

Apparently a common feature of modern life--''late to bed, early to rise''--will definitely not make an individual ``healthy and wise.''

Researchers have found that overnight sleep loss provokes an almost immediate rise in sleep-inducing hormones, leaving the individual to wage a battle of will to stay awake against a rising wave of sleepiness.

``One night of sleep deprivation can elicit significant physiological changes the next afternoon...(and) having to cope with staying awake despite increased sleepiness would lead to psychological stress,'' report a team of researchers based in Singapore.

The researchers--led by Victor Hng-Hang Goh of the Department of Obstetrics and Gynecology at the National University of Singapore--focused on 14 healthy men between the ages of 20 and 30 who were active members of the Singapore Armed Forces.

The men were divided into two groups, the first of which slept a full eight hours. The others remained awake all night. Saliva samples were taken and strength and motor skill tests were conducted with all the men before and after the evening of sleep deprivation.

In the current issue of Military Medicine, Goh and his team noted that those men deprived of adequate sleep produced a much higher level of the hormone melatonin than those whose sleep pattern was not disturbed.

Melatonin is a hormone that plays an important role in regulating sleep. The hormone is sleep-inducing in some people.

The researchers further found that levels of cortisol--a hormone associated with increased stress--did not rise to higher levels among the sleep-deprived men then among those who slept normally. However, an indirect cortisol connection was in evidence, as Goh and his colleagues noted that those with inadequate sleep who experienced the stress of trying to stay awake did display increased cortisol levels along with peak melatonin increases--both around 1:30 in the afternoon.

While short-term sleep deprivation did not appear to affect the men's ability to perform tasks involving either motor control or strength, the researchers concluded that losing just eight hours of sleep does have a real and immediate effect on an individual's state of mind and feelings of fatigue.

``One complete night of sleep deprivation is as impairing in simulated driving tests as a legally intoxicating blood alcohol level,'' commented Mark Mahowald, the director of the Minnesota Regional Sleep Disorder Center at Hennepin County Medical Center in Minneapolis. While not associated with the Singapore study, Mahowald--a professor of neurology at the University of Minnesota Medical School and a member of the American Academy of Sleep Medicine--expressed little surprise at the findings.

``What most people do not realize is that literally any degree of sleep deprivation will decrease performance,'' Mahowald told Reuters Health. He added that anyone who uses an alarm clock to wake up is by definition sleep-deprived--and that the study findings may help to drive home the biology behind the need to sleep which modern culture works so hard to ignore.

``Sleepiness is treated as a sign of depression, laziness, slothfulness and work avoidance behavior,'' he said. ``And God forbid you take a nap. If I fell asleep when you were talking to me you would be annoyed. But if I had a seizure you would say 'wow this guy has a medical problem and needs some help.' Sleep is not negotiable. It's a biological imperative. And we are hopefully coming to realize that a lack of sleep exacts a major toll.''

SOURCE: Military Medicine 2001;166:427-431.