A good night’s sleep is probably the most underappreciated element of a healthy lifestyle. Sleeping is essential for human health, and sleeping is usually regulated by the dark-light cycle. We tend to sleep better when it’s dark and not so well when it’s light. But in our modern life, light doesn’t only come from the sun.
Street lights, cars, electronics, they all produce light than can disrupt our sleep, even if we don’t realize it. In fact, a new study suggests that eliminating all light during sleep can be very helpful.
For the lead author, this study was personal.
“Moving to the United Kingdom meant not being able to sleep for a simple reason: houses in Cardiff don’t have shutters!” said study author Viviana Greco, a PhD candidate at Cardiff University Brain Research Imaging Centre. “Most houses in the Cardiff area have only curtains and even blackout curtains are not enough to provide complete darkness.”
Greco and her colleagues wanted to see how much of a difference an eye mask could make. Some studies have suggested that eye masks can help patients sleep better in a hospital setting, the effect on sleeping inside your home is less understood. So, Greco and colleagues carried out two studies.
In the first one, 89 participants aged 18-35 spent 5 nights sleeping at home with an eye mask and 5 nights sleeping at home without an eye mask. After both bouts, they underwent two days of testing.
When people slept with an eye mask, they reported better overall sleeping. They also reported better attention and alertness levels after sleeping with an eye mask. They even performed better on learning performance (as highlighted by a word-pair association task).
The second experiment included 33 participants, also aged 18-35. This time, they wore an eye mask for two nights and an eye mask with cutouts so that no fabric covered the eye. This was meant to control whether it’s somehow the headband itself and not the light-blocking that was having the effect. Participants wore an EEG headband while sleeping.
This confirmed that participants were sleeping better when the fabric was specifically covering their eyes.
The study has significant limitations. With 89 participants in the first study and 33 in the second, the sample sizes are relatively small. This limits the generalizability of the results. In addition, the study period was pretty short, and the effects may attenuate (or not) over longer periods of time. Since the study was conducted in Cardiff, cultural or regional factors may affect the generalizability to other populations.
Nevertheless, the findings suggest that wearing an eye mask during overnight sleep can improve episodic encoding and alertness the next day — which has important, real-life implications.
“Overall, our findings suggest that a simple manipulation — the use of an eye mask during sleep — can lead to superior memory performance and higher alertness the next day,” the researchers write in the study. “These findings have broad implications for the performance of the many daytime tasks that require learning in educational and cultural contexts, in which particularly effective encoding will determine opportunities for growth, as well as a fast response to external stimuli. Given the current climate of life-hacking, sleep monitoring, and cognitive enhancers, our findings suggest the eye mask as a simple, economical, and noninvasive way to get more out of a night of sleep.”
It’s striking that something as simple as an eye mask could be a low-cost, non-invasive tool to improve not just sleep, but potentially our day-to-day alertness and learning ability as well. While the research does have its limitations, and more extensive studies are needed to confirm these results, the initial findings are promising.
The study was published in the journal Sleep.
