$10 purchase can improve sleep, boost brain

Your bedroom is probably not as dark as it should be. Even through closed eyelids, light streaming from the television or hallway can make its way into our retinas and harm our health and mental acuity the next day.

The deleterious health effects of nighttime light exposure are staggering.

Research has shown that even relatively dim light when we snooze — about the equivalent of a hallway light — can have surprisingly profound physiological effects, raising heart rates, reducing the duration of important sleep stages and increasing insulin resistance. In older adults, any light exposure at night was associated with higher rates of obesity, diabetes and hypertension.

Thankfully, there is a simple solution: Wear an eye mask when you sleep.

Wearing an eye mask to sleep is “very basic and simple,” said Viviana Greco, who conducted a study on the topic as a neuroscience and psychology graduate student at Cardiff University, and now works at Neuronatch, a neuroscience nonprofit. “At the same time, it can have huge benefits.”

Cognitive and health effects of eye masks

“Light at night is telling the brain ‘danger, danger,’” because the brain isn’t expecting it. This may rev up the brain’s autonomic “fightor-flight” system, which could make it harder to go into deep sleep, said Phyllis Zee, a neurologist and director of the Center for Circadian and Sleep Medicine at Northwestern University’s

Feinberg School of Medicine.

Zee also said that because many people work indoors, they get less bright light during the day, which can make a person more sensitive to light at night.

But several studies have shown that simply covering the eyes at night can make a difference. Research conducted primarily with hospital patients trying to sleep through the blinking lights and whirring noises of medical equipment reported that wearing an eye mask (and ear plugs) improved subjective sleep quality. Another study found that wearing an eye mask could help pregnant women by improving sleep quality and duration compared with other pregnant women given a pamphlet on better sleep.

Now, a study published in the journal Sleep has reported that wearing an eye mask at night could improve memory and alertness in the morning. The study comprised two experiments. In the first experiment, 89 participants ages 18 to 35 slept with an eye mask for two consecutive weeks in the summer, when the sun rose as early as 5 a.m.

For one week, they wore an eye mask that could block light; for the other week, they wore a mask with eyeholes cut out (akin to those worn by cartoon burglars) so no light would be blocked.

The subjects were instructed to go to bed at the same time each night, abstain from alcohol and strenuous physical exercise, and sleep with the curtains open. Crucially, none had slept with an eye mask before.

They had five nights of getting used to the eye mask each week, but in the mornings after the sixth and seventh nights, Greco and her colleagues gave the participants a battery of cognitive tests.

The tests showed that wearing the regular eye mask improved memory — participants could remember more pairs of words. Wearing an eye mask also improved their reaction time on a standard vigilance test. There was no difference on a third test for motor-skill learning.

In the second experiment, 35 participants wore an EEG headband to monitor their sleep in addition to the eye mask.

While wearing an eye mask did not alter their overall sleep, there was a positive correlation between participants’ performance on the memory test and the amount of time they spent in slowwave sleep, which is a sleep stage known to be important for memory.

“It’s a really good study that shows you the effect of light on sleep,” Zee said. The study is novel because it shows that blocking light at night could improve daytime performance and that this was related to slow-wave sleep, she said.

While the study did not find a subjective change in the participants’ sleep quality, this may be because the individuals in this study are very healthy, so the results might not be easily generalizable, Zee said. Light at night may be more detrimental for less healthy individuals, who may stand to benefit more from an eye mask; others may find a mask too uncomfortable to wear.

Overall, this study shows that an eye mask to block the light is a practical solution for those who may not be able to sleep in a dark environment, such as if you have children, night lights or streetlights, she said.

How to manage light at night

• Find an eye mask that is comfortable and fits. Greco gave study participants an eye mask with an elastic band for easy adjustment. She says she prefers fluffy ones that are more soft and comfortable.

• Darken your bedroom. Switch off extraneous lights. Zee said she has covered indicator lights on devices with electrical tape. Blue light should be especially avoided.

• Put away electronic devices. It will help you avoid notifications and other distractions. You are training yourself to learn that “this is your time for sleep and just try to go to sleep,” said Greco, who puts her phone and laptop in another room to avoid distractions.

• Try blinds or blackout curtains. Zee said she only uses an eye mask when she sleeps on a plane but has blinds at home. (Zee said she has blinds that can be electrically opened without her getting out of bed in the morning.) Blackout curtains also can be helpful, though they may make it difficult to get morning light.

• Get more light during the day. Reducing light at night is just one part of a healthy light diet. “As a doctor, I tell my patients if you cannot be in the dark” at night, “then make sure you get more light during the day,” which can partially offset the detrimental effects of light at night and improve sleep, Zee said.