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01-11-2006, 12:33 PM
Morning grogginess like being drunk

Published: Wednesday, January 11, 2006

For anyone who has ever made coffee in the morning and forgotten to put the pot under the drip spout comes comforting news: morning grogginess impairs the brain as much as being drunk.

Scientists who tested the effects of "sleep inertia" -- the blurry thinking and disorientation that occurs when we first wake -- found volunteers performed even worse on a thinking and memory test immediately after being roused from a sound, eight-hour sleep than they did when they went 26 hours without sleep.

Earlier studies have shown 24 hours of sleep deprivation impairs everything from simple reaction times to complex decision-making as much as having a blood alcohol of 0.08, the point of legal impairment.

The new study didn't compare morning grogginess to alcohol intoxication. But the volunteers' cognitive performance immediately upon waking "was worse than anything we see after being awake for 26 hours," said lead author Kenneth Wright.

"For a short period, at least, the effects of sleep inertia may be as bad as or worse than being legally drunk," he said in a release.

"When you first wake up, you are severely impaired. We can say that with confidence," he said in an interview.

The most severe effects on thinking occurred within the first three minutes of waking. Within 21 minutes, those severe impairments were gone, but other effects were still detectable for up to two hours.

The study, published as a research letter today in the Journal of the American Medical Association, involved just eight men and one woman. But the researchers say the results are robust and backed by biology.

"When we first wake up, the brain doesn't just go from zero to 60 quickly. It takes a little while for our brain to make that transition from sleep to alert wakefulness," says Wright, director of the sleep and chronobiology laboratory at the University of Colorado in Boulder, Co. And the prefrontal cortex, the part of the brain behind the forehead that controls complex thinking, takes longer to come "online" than other brain areas.

The results could have implications for paramedics, police, doctors and firefighters who get roused from sleep and have to rush to an emergency scene, and for long-haul truck drivers. Medical residents who nap during shifts could easily make a mistake calculating drug dosages during bouts of sleep inertia, Wright says.

"We need to recognize that this phenomenon occurs. It might be important that someone else is making critical, important decisions until this person has been able to wake up."

It also shows why it's so important to have a fire escape plan. "Not only do you have to think about where you're going to go out if you haven't planned that already, that thinking ability is going to be impaired" when the alarm goes off.

Sleep inertia is one of the reasons why people reach for that morning cup of coffee, even though the inertia will dissipate unaided given time.

Wright and researchers at Harvard Medical School in Boston studied nine volunteers, aged 20 to 41. The volunteers slept for about eight hours a night for three weeks, then lived in a sleep lab for a week.

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