Apparently, caffeine can only do so much.
Reaching for a daily cup of joe to get going in the morning ceases to be effective after too many late nights, according to the American Academy of Sleep Medicine.
A study supported by the U.S. Department of Defense Military Operational Medicine Research Program found that coffee loses its punch after three days of poor rest.
Participants, who were restricted to five hours of sleep a night for three days, were given either 200 milligrams or a placebo twice a day. Testing showed that performance on psychomotor vigilance tasks, such as reaction times, improved with caffeine during the first two days of short sleep but not the third.
“We were particularly surprised that the performance advantage conferred by two daily 200 milligram doses of caffeine was lost after three nights of sleep restriction,” says Tracy Jill Doty, lead author and 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.”