Science Probes the Awakening Brain

The mind stays sluggish in the first 10 minutes after sleep ends, research finds

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By Randy Dotinga
HealthDay Reporter

TUESDAY, Jan. 10, 2006 (HealthDay News) -- Americans who check their e-mail and scan the newspaper right after they get out of bed in the morning may want to wait just a bit longer.

That's the message from a small study that suggests the brain needs a little time to wake up.

In fact, researchers found that people who just wake up from sleep are more mentally addled than when they undergo 26 hours of sleep deprivation.

"It takes some time until we're able to be efficient in our ability to make decisions and think clearly," said Kenneth Wright Jr., director of the Sleep & Chronobiology Lab at the University of Colorado at Boulder. He's the co-author of a study appearing in the Jan. 11 issue of the Journal of the American Medical Association.

In most instances, the type of post-sleep "brain fog" noted in the study wouldn't seriously affect a person's ability to perform. However, people do need to think fast and clearly in emergencies, and Wright said the research could be especially relevant for firefighters and other individuals who need to function at their best soon after awakening.

To better understand "sleep inertia," Wright and colleagues recruited nine men and one woman, with an average age of 29, and made them take mathematical addition tests several times in the hours after waking from sleep. They also took the tests after being kept awake for 26 hours.

The researchers found that the subjects did more poorly on the tests in the moments just after waking from a normal night's sleep. "We thought that (their performance) would be just as bad as sleep deprivation, but we were a little surprised that it was worse," Wright said. "The serious effects are probably gone within the first 10 minutes, but we still can detect impairments for up to two hours."

Why does sleep have this effect? Researchers aren't sure, said Dr. Robert Vorona, an assistant professor of sleep medicine at Eastern Virginia Medical School. "Although sleep inertia is ubiquitous, it has not been extensively studied and its cause is not clearly understood."

What's next? Researchers would like to figure out how long it takes for people to think and function clearly after waking, Wright said. "We're also interested if someone is under a very intense emergency, does that emergency affect how long it takes for the brain to wake up?"

That could be a vital question for people like doctors -- who are often woken up in the middle of the night to make important decisions -- or firefighters who must suddenly run out to fight a fire, Vorona said.

Ultimately, emergency workers may need to take the research into account when they figure out who makes major choices in a crisis, Wright said. "It may be more important for someone else to make those decisions until someone [who's just woken up] has gotten past that initial impairment."

And what of America's favorite wake-up beverage, coffee? The researchers didn't examine its brain-stimulating effects, but Wright said researchers have discovered that consuming caffeine before a nap actually helps people be more alert upon waking. The key, he said, is not to consume too much so that you can't sleep in the first place.

More information

Learn more about sleep inertia from the University of Denver.

SOURCES: Kenneth P. Wright Jr., Ph.D., assistant professor, Department of Integrative Physiology, and director, Sleep & Chronobiology Lab, University of Colorado at Boulder; Robert Vorona, M.D., assistant professor, sleep medicine, Eastern Virginia Medical School, Norfolk; Jan. 11, 2006, Journal of the American Medical Association

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