Coffee’s powerful effects diminish after three night’s of bad sleep
Two doses of coffee a day has been found to boost performance. However caffeine junkies shouldn’t get too excited, as researchers have found its powerful effect stops if the drinker has had three consecutive nights of bad sleep.
Getting a poor night’s rest means many people will reach straight for the coffee maker come sunrise, but scientists from the Walter Reed Army Institute of Research in Washington, America, discovered it’s not such a fool proof fan.
They looked at a group of 48 healthy individuals who weren’t allowed to sleep for more than five hours a night (deemed restricted sleep) for five days in a row. The team was split into two; one group consumed 200mg of caffeine twice a day, the other drank a placebo alternative. They then had to undergo tests, including a Psychomotor Vigilance Task (PVT), a profile of mood, the Maintenance of Wakefulness Test and the Stanford Sleepiness Scale.
The results, published journal Sleep, showed that while caffeine initially boosts performance, it wears off after three consecutive nights of restricted sleep.
“We were particularly surprised that the performance advantage conferred by two daily 200mg doses of caffeine was lost after three nights of sleep restriction,” lead author, Dr Tracy Jill Doty 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.”