Blocking out ambient light while you’re slumbering can improve alertness and memory the following day, according to a study involving 122 participants over two experiments, the findings of which were published in Sleep.
The study authors, from institutions in the UK, Italy, and the US, say that this is further evidence of the link between light and sleep – and that controlling the former can help in managing the latter.
“Ambient light can influence sleep structure and timing,” write the researchers in their published paper.
“We explored how wearing an eye mask to block light during overnight sleep impacts memory and alertness, changes that could benefit everyday tasks like studying or driving.”
In the first experiment, 89 adults aged 18 to 35 were asked to wear an eye mask while sleeping for a week, before going without it, or wearing an eye mask with holes (to factor in any effects from the discomfort of wearing a mask) the week after.
Lab tests carried out on the last two days of each week showed that the participants performed better on a word-pair association task, which measures the ability to recall events and experiences, after having their eyes covered while sleeping. They also performed better on a test that measures reaction times.
For the second experiment, 33 adult volunteers aged 18 to 35 were equipped with eye masks, devices to measure the light intensity on waking, and a wearable headband to measure brain activity while they slept.
To get used to the conditions, the participants slept with an intact eye mask one night and an eye mask with holes with holes for the second night. This was followed by two nights’ of sleep under the same conditions, only this time with added testing.
Again, a word-pair association task revealed wearing an eye mask helps with learning new information and forming fresh memories. In addition, data provided by the headband suggests there is an association between mask wearing and more slow-wave sleep time, known to be important when it comes to memory boosts.
“The benefit to memory was predicted by time spent in slow-wave sleep while wearing the mask,” write the researchers.
“This suggests wearing an eye mask during sleep is an effective, economical, and non-invasive behavior that could benefit cognitive function and lead to measurable impacts on everyday life.”