Hate to break it to you, caffeine junkies: Coffee might feel like the Elixir of Life when you’re sleep-deprived, but research says that eventually the magic fades, and you really should just hit the sack. A study presented at the 2016 meeting of the Associated Professional Sleep Societies held in Denver found that:
After just three nights of bad sleep, caffeine stopped boosting alertness, performance and mood.
The findings further underscore that “sleep debt is real,” says Tracy Doty, the research scientist at Walter Reed Army Institute of Research who led the study. “Every night you’re not sleeping, you’re building up increased sleep debt, and the same amount of caffeine is no longer effective.”
Earlier studies on the effects of caffeine on performance had typically kept subjects awake all night for multiple nights in a row. But Doty wanted to mimic a workweek, restricting sleep to five hours a night (less than the recommended seven to nine hours a night) for five nights. Doty’s team recruited 48 healthy adults who slept 10 hours a night for five nights in the lab to ensure they started at the same baseline level. The following week, the researchers restricted their sleep, flipping the lights on after five hours.
