WASHINGTON – Of all the things that affect American productivity,scientists say there's one simple culprit – sleep deprivation and the absence of a mid-day siesta.
On any given day,almost three quarters of a million high school students – 737,296 or 28 percent – fall asleep in school,said Mary A. Carskadon,professor of psychiatry and human behavior at Brown University,at a sleep conference Tuesday. Six percent of middle school students,more than 100,000,fall asleep at school each day.
The National Sleep Foundation,a nonprofit organization dedicated to promoting public awareness about nocturnal health,hosted the conference.
Teenagers experience a change in sleep rhythms during puberty,naturally tending to stay up later at night and get up for school with fewer hours of shut-eye.
Phyllis C. Zee,an associate professor of neurology,neurobiology and physiology at the Northwestern University School of Medicine,said teenagers try to recover from early school start times by sleeping in on weekends.
Several researchers at the conference noted that studies show naps offer a significant possible benefit to the sleep-deprived masses.
“I don't think we were meant to be uni-phasic sleepers – to crunch everything into one night,” Zee said. “If we were allowed,we would become bi-phasic sleepers. But that's just my opinion.”
When Americans don't get enough sleep,conventional wisdom says caffeine helps. Caffeine is used by 90 percent of North Americans on a daily basis,according to Sara C. Mednick,assistant professor of psychiatry at the University of California at San Diego. But,she said,the drug is not a good a substitute for sleep.
Mednick,who lectures around the country about naps,wrote in her research, that caffeine impaired some types of learning and verbal memory in sleep-deprived subjects. In contrast,an afternoon nap improved recall and learning.
Babies generally sleep about 14.5 hours each day. By age 12,they need about nine hours. Adults require seven to eight hours.
“Cognitive decline” in the elderly can be at least partially explained by lack of sleep, Zee said. In tandem with poor health and sleep disorders,the elderly are often caught in a chronic cycle of sleep deprivation.
Each year NSF sponsors a survey about American sleep habits. Out of 1,000 respondents this year,89 percent said they do not nap at work. Blue collar workers – 15 percent of them – are slightly more likely than white collar workers – 9 percent – to say that they have taken a nap at work. About a third of workplaces allow employees to nap during breaks,and 16 percent provide a nap place.
The survey's margin of error is plus or minus 3.1 percentage points.
In all of its versatility,the human brain is able to activate new areas when it is sleep deprived,according to a study by Sean Drummond,assistant professor of psychiatry at UCSD.
These areas are used more intensely than normal and help with learning and memory. Drummond took images of sleep-deprived brains as people were memorizing lists of easy or difficult words. His studies found that sleep-deprived brains activated the new areas when presented with harder cognitive tasks.
With increased amounts of deprivation,however,the subjects' brains were less able to cope,even with the additional activated areas.
“In every single study,there are always individuals that show perfectly intact learning abilities,no matter the lack of sleep,” Drummond said.
Even in older adults,some individuals seem unfazed by sleep deprivation.
Drummond said scientists need to find a better way to predict who will be affected.
“Gender doesn't predict it. Age doesn't entirely predict it. So what does?” Drummond asked.
It's harder for affected students to catch up with a snooze during the day.
Carskadon said schools have failed in important ways,such as not teaching about sleep in the classroom and making teenagers rise early in the day,against inclinations set by their biological clocks.
“Blaming the victim,the high school student,asking them to get up at 6 a.m. to catch the bus for school at 7 or 7:30,making them go to bed at 7:30 at night,in 2008 is an untenable position,” she said. “It's not fair and it doesn't make sense.”
Asked what time would be reasonable,Carskadon responded,”I don't have a magic bullet answer. But I can tell you,7 o'clock is too damn early.”