Chronically Sleep Deprived? Coffee Won't Help You

Most people count on coffee – or another form of caffeine – to keep them awake, but if you’ve gone without enough sleep for more than two day it won’t help, a new study shows.

Researchers from the American Academy of Sleep Medicine conducted an experiment using 48 healthy people. They restricted their sleep to five hours of time in bed for a total of five days.  The participants were administered either 200 mg of caffeine  (about the amount in two cups of coffee) or a placebo.

The participants were divided into two groups, one that was administered 200 mg of caffeine, and the other a placebo.  Then, during their waking periods, the researchers administered a battery of tests, including the psychomotor vigilance tests (PVT), which is the classic test given to measure alertness, along with thinking tests, and evaluations of mood and sleepiness. In addition, a modified version of a test that measures wakefulness was administered six times daily.

The results showed that the caffeine significantly improved the PVT tests during the first two days, but not the last three days of sleep restriction.

"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," said lead author 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,” she said of the study, which was presented this week at SLEEP 2016 in Denver, Colo.