Scientists give the nod to more sleep time.

Scientists give the nod to more sleep time

Now you don't have to feel guilty when you hit the sleep button to quiet the early-morning blast of your clock radio. New research suggests healthy people who sleep an extra hour or two are more wakeful during the day and perform better on tests measuring reaction time and vigilance.

This finding supports the theory that many people live with a chronic "sleep debt," which builds during the work week and is relieved in part by lazy weekends. The research, described in the October SLEEP, shows that extra sleep can yield a performance boost, especially for people more sleep-deprived than most.

At Henry Ford Hospital's Sleep Disorders and Research Center in Detroit, Timothy Roehrs, Thomas Roth and their colleagues studied healthy men aged 21 to 35 who had regular bedtimes and normal sleep patterns. At the study's start, they gave volunteers the Multiple Sleep Latency Test (MSLT). Administered four times a day, the test assesses daytime wakefulness by measuring how quickly subjects fall asleep when instructed to nap in a dark room. The researchers used MSLT scores to identify 12 men who were sleepier than, average and 12 who are more wakeful than average.

They then had the 24 subjects spend one eight-hour night in the sleep laboratory, sending them to bed at 11:30 p.m. and waking them at 7:30 a.m. For the next six nights, participants went to bed two hours earlier. The men slept in the laboratory on nights 1, 3 and 6 of this phase.

On each day following a night in the sleep lab, the researchers gave study participants the MSLT, waking them 90 seconds after they fell asleep to prevent the naps from adding to total sleep time. On the same days, the men took tests that measure reaction time and sustained vigilance--abilities needed for such tasks as driving car or monitoring nuclear power-plant equipment.

The scientists found that when the men spent 10 hours in bed, they typically slept for nine hours and showed more alertness during the day. The 12 who were the sleepiest at the study's start, nodding off after six minutes or less during the initial MSLT naps, improved the most.

By the last day of the sleep-extension part of the study, the average score for this subgroup had risen to 10 minutes. The normally alert subjects -- who appeared less sleep-deprived to begin with -- improved slightly, taking at least 16 minutes to fall asleep during the initial MSLT and an average of 18 minutes on the last day. Both groups scored higher on attention and vigilance tests after spending 10 hours in bed.

The researchers say their study dispels the notion that too much sleep is detrimental to performance. "Most people will benefit from spending more time in bed," says Roth. "Ideally, you should sleep until you're slept out," Roehrs adds. But getting more sleep in today's fast-paced world may not be easy, they note.

James A. Horne, a sleep researcher at Loughborough University in Leicestershire, England, contends the benefits seen in this study are "marginal" and may not be worth the trouble for most individuals. "They are talking about two hours' extra time in bed for a small improvement in reaction time," he says. Horne disputes the theory that most people are sleep-deprived, arguing that people tend to sleep in on weekends not out of biological need but because sleeping late is a pleasant experience.