Researchers from Cardiff University in the U.K. have found that blocking out as much light as possible while sleeping improves alertness the following day. In the study they had participants wear eye masks to bed for several nights, then did the same number of nights sleeping without a mask. They slept in their own homes to make sure they were getting real-life sleeping scenarios and they kept a sleep diary to record their experience with and without the mask.
After waking up, participants took three different tests to measure brain power. And while the masks didn’t make a difference in the amount or quality of sleep they got, people did better on cognitive tests and reaction time exercises during the week they slept in eye masks. Researchers believe the masks help sleepers spend more time in the deepest phase of sleep, which is important for processing new information. Study author Viviana Greco says wearing an eye mask could be “an effective and inexpensive solution” to boosting alertness and work performance.