It’s well established that caffeine boosts alertness and performance. But for how long?
Caffeine does not improve alertness or performance after three nights of restricted sleep (5 hours sleep per night), recent research finds.
Compared to a placebo, caffeine significantly improved Psychomotor Vigilance Task (PVT) performance during the first 2 days of sleep restriction, but not the last 3 days of sleep restriction.
The study’s lead researcher, Dr. Tracy Jill Doty, of Walter Reed Army Institute of Research said:
These results are important, because caffeine is a stimulant widely used to counteract performance decline following periods of restricted sleep.
The data from this study suggests that the same effective daily dose of caffeine is not sufficient to prevent performance decline over multiple days of restricted sleep.
The double blind, placebo-controlled study involved 48 healthy people.
Sleep was restricted to five hours of time in bed for a total of five days.
Participants were given either 200 mg of caffeine or a placebo twice daily.
Researchers administered a cognitive task battery hourly during the wake periods, including a:
– 10-minute PVT;
– Profile of Mood States (POMS); and
– the Stanford Sleepiness Scale (SSS).
Researchers also administered a modified Maintenance of Wakefulness Test (mMWT) six times per day.
The research abstract was published in an online supplement of the journal Sleep
Image credit: Flickr