Study shows impact of sleep loss, deprivation

If you're feeling sleep-deprived -- or even just a little tired -- the chances are that your body is more tired than you might actually think.

According to a study by Penn psychiatry professors published this week in the medical journal Sleep, while chronically sleep-deprived people report feeling only "slightly sleepy," they can in fact be at their lowest physical and psychological functionality levels.

The research further explains that people who regularly receive six or fewer hours of sleep each night have significant decreases in normal cognitive and neurobehavioral capabilities.

"You can't rely on people to judge their own performance capabilities and sleepiness if they are sleep deprived," said Hans Van Dongen, author of the study and professor of sleep and chronobiology in the Psychiatry Department.

"Some people need more sleep than others," Van Dongen said. "It's better to be safe and get more sleep."

Van Dongen worked in conjunction with David Dinges, a psychology professor in the Psychiatry Department and chief of the Division of Sleep and Chronobiology, statistician Greg Maislin and Harvard professor Janet Mullington.

The 14-day study brought 48 people into the lab for 24 hours each day and restricted certain groups to four-hour, six-hour, and eight-hour nights of sleep. The healthy adult volunteers, some affiliated with the University, ranged in age from 21 to 38, and were strictly monitored each day for objective measurements, such as sustained attention levels, working memory and ability to multitask.

As the sleep debt accumulated each day, the ability to perform the objective measurements decreased, while the subjective measurements, such as one's sleepiness, did not. The study therefore concluded that people are unable to judge their own tiredness and are unaware of their own decreased cognitive performance, Van Dongen said.

While the best method for sleep deprivation recovery is more sleep, Van Dongen suggested that "caffeine on a limited, occasional basis is a good countermeasure."

Van Dongen sees the findings of the study as important to people in a variety of occupations whose jobs sometimes require them to receive minimal amounts of sleep, such as military personnel, medical residents, parents of young children and students.

For students, "the most important thing to realize is the value of sleep," Van Dongen said. "It is not a waste of time."

College freshman Matt Weil is one of many students who recognizes the necessity of getting enough sleep.

"Without sleep, it's hard to work in class," Weil said. "I can't concentrate on my homework."

To the weary-eyed, Van Dongen offered a glimmer of hope, suggesting that "sleeping in on the weekend" is an effective method of sleep debt recovery.

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