We've all been there. Those times when there really aren't enough hours in the day — whether it's traveling, working, studying, new babies or old illnesses, sometimes you just aren't going to get enough sleep. But there are always tricks to get you through the day, aren't there? Coffee is your friend, right? As it happens, not so much. A new study suggests that, when sleep is restricted to five hours per night for three nights, caffeine no longer improves alertness or performance.
Results showed that, when compared to a placebo, caffeine significantly improved Psychomotor Vigilance Task (PVT) performance during the first two days, but had little effect after three days of sleep restriction. A PVT test checks alertness by measuring subject response times. The new research abstract was published recently online by the journal Sleep.
"We were particularly surprised that the performance advantage conferred by two daily 200 mg doses of caffeine was lost after three nights of sleep restriction," says lead author Dr. Tracy Jill Doty, research scientist at Walter Reed Army Institute of Research. "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 study group consisted of 48 healthy individuals who participated in a double blind, placebo-controlled study. The "double blind" method ensures that neither the participant nor the observer know whether a placebo or a real drug has been administered. Sleep was restricted to five hours in bed for a total of five days and participants were given either 200 mg of caffeine or a placebo twice daily. The participants were set a series of cognitive tests hourly during the wake periods — these included a 10-minute PVT and Profile of Mood States (POMS). A modified Maintenance of Wakefulness Test (mMWT) was also given.
Despite what advertisers tell you, your body is a delicate machine, not something that should be constantly kick-started with a zap of energy. The side effects of caffeine when taken to excess are serious and can lead to permanent health issues. If you're feeling a little sluggish, why not check out these 30 high-energy alternatives to caffeine or our 7 ways to turbocharge your morning without a ton of coffee.