Most Use Caffeine Wrong, Study Suggests
More Alertness From Hourly Espressos Than Morning Mugs
May 11, 2004 -- Small shots of coffee throughout the day keep you more alert than morning mugs of joe, researchers find.
An Air Force-funded study shows that coffee really does keep a person alert -- but only if used the right way. Study leader James Wyatt, PhD, is a sleep researcher at Rush University Medical Center.
"I hate to say it, but most of the population is using caffeine the wrong way," Wyatt says in a news release. "Drinking a few mugs of coffee or tea in the morning ... means that caffeine levels in the brain will be falling as the day goes on. Unfortunately, the physiological process they need to counteract is not a major player until the latter half of the day."
If you have to stay alert and fight off sleep, one or two jolts of java just won't do the trick. Wyatt's team finds that it's better to take tiny amounts of caffeine -- about two ounces of coffee -- every hour, all day long.
Why? The body has two ways to make you sleep. One is your built-in, 24-hour circadian clock. This makes you feel sleepy at night and wakeful during the day. The other sleep mechanism is a steady build-up of chemical messengers that bring sleep closer and closer the longer you stay awake. Caffeine blocks these chemical messengers and staves off sleep, Wyatt and colleagues suggest.
No matter how you take it, caffeine is no substitute for a good night's sleep. People who tried this caffeine regimen did perform better. But they paid a price: Despite their enhanced wakefulness, they felt sleepier than people not taking caffeine. By taking small, frequent caffeine doses they did, however, avoid the jitteriness and other side effects of larger doses.
The 42.85-Hour Day
For their study, Wyatt and colleagues signed up 16 healthy men aged 18 to 30. After keeping away from alcohol, caffeine, and medications for at least two weeks -- and after keeping to a strict eight-hour sleep schedule for three weeks -- the men spent a month at a sleep lab.
In the lab, the men stayed in a special suite with no windows and no way to tell what time it was. To keep their internal clocks from keeping time, the men kept 42.85-hour days. They stayed awake for 28.57 hours -- during which they performed frequent tests -- and slept for 14.28 hours.
These wacky hours mimic the effects of an all-nighter -- or the kinds of work shifts common for military personnel, emergency workers, and hospital house staff.
Starting one hour after they woke up, eight of the men took a caffeine pill equivalent to 0.3 mg of caffeine per kilogram of body weight every hour. The other eight men took a placebo. Neither they nor the researchers knew who was taking which pill until the study was over.
As their long days wore on, the men who got no caffeine did worse and worse on various tasks. But men taking the frequent small doses of caffeine -- roughly the same as a two-ounce shot of coffee -- did much better on these tasks, although their performance also dropped off a bit over time.
"Our results highlight the impairments in cognition that accompany all work schedules that lie outside the usual 9 to 5 workday," Wyatt says. "In addition, they reveal an entirely new way to use caffeine to maintain alertness and performance in the face of sleep loss."
The study appears in the May issue of the journal Sleep.