Looks like coffee can only keep us alert and happy for so long.
According to research presented at the SLEEP 2016 Conference, coffee leads to more harm than good if you are constantly sleep-deprived.
Study participants were instructed to sleep for 10 hours a night over a five-day period, according to the American Academy of Sleep Medicine. After which, the 48 individuals were limited to sleeping a mere five hours a night.
Half of the group received 200 milligrams of caffeine twice daily, which is the amount in a cup of strong coffee, while the rest of the participants were given a placebo. Both groups were presented with various tests to measure their mood, cognitive abilities, and wakefulness.
Based on the results, the caffeine was only effective for the first two days of sleep deprivation. After that, it was no more effective than the placebo.
"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 Dr. Tracy Jill Doty, lead author of the study 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," Doty continued. "The data from this study [suggest] that the same effective daily dose of caffeine is not sufficient to prevent performance decline over multiple days of restricted sleep."
Furthermore, the participants in the caffeine group also said their mood was greatly affected over the course of the study. In fact, it appears that it’s better not to consume caffeine regularly if happiness is important to you.
"Likewise caffeine effectively increased sleep latencies and improved ratings of happiness only for the first few days of sleep restriction," Doty explained, as reported by The Telegraph. "In fact over the final days of SR those in the caffeine group rated themselves more annoyed than those in the placebo group."
As coffee has been forever deemed as possessing energy-boosting powers, more research needs to be done to determine the long-term effects of this reported misconception.
Or maybe, just maybe, we could try to get more sleep.