Too much light in your bedroom? Using a sleep mask helps you avoid light exposure at night and can have a significant effect on your memory and alertness.
- By using a sleep mask at night, your memory and alertness may improve
- Study participants were better able to recall events and experiences, and had improved reaction times, when they wore a sleep mask at night
- Wearing a sleep mask enhanced participants’ ability to learn new information and form memories
- Use of sleep masks, as well as ear plugs, by ICU patients significantly improved subjective sleep quality
- Exposure to light at night may increase your risk of cancer, obesity, high blood pressure and diabetes
Sleep masks provide an economical, DIY solution to get the darkness your body requires for optimal sleep, and just by wearing one nightly your memory and alertness may improve. The finding came from research published in the journal Sleep,1Sleep December 15, 2022 which underscored that sometimes the simplest interventions have the most powerful effects on health.
This certainly seems to be the case for sleep masks. Blocking out ambient light at night is essential to a good night’s sleep — and all of its related benefits — but it can be difficult to make your bedroom pitch black. Sleep masks provide a different means to the same end — a dark environment that’s conducive to restful, restorative sleep.
Wear a Sleep Mask to Boost Memory and Alertness
In the first experiment of a two-part study, 89 adults aged 18 to 35 wore an eye mask while sleeping at night for seven days, followed by a period of not wearing an eye mask during sleep and then wearing an eye mask with holes in it, which allowed light to pass through.2Science Alert March 1, 2023 The participants slept with the eye mask for five nights to get used to it before researchers conducted cognitive tests on the sixth and seventh days.
“Superior episodic encoding and an improvement on alertness”3Sleep December 15, 2022 was noted when the participants wore the light-blocking sleep mask. They performed better on a word-pair association test, which measures the ability to recall events and experiences, as well as a test to measure reaction times.4Science Alert March 1, 2023
For the second part of the study, 33 people aged 18 to 35 slept with an eye mask one night followed by an eye mask with holes the next night. They also wore a headband to measure brain activity and used a device to measure light upon waking. The cycle was then repeated, with researchers again conducting cognitive tests.
Not only did the light-blocking sleep mask enhance participants’ ability to learn new information and form memories, but it was associated with more slow-wave sleep (SWS), which may be beneficial for memory.5Science Alert March 1, 2023 The researchers explained:6Sleep December 15, 2022
The synaptic homeostasis hypothesis posits that SWA [slow-wave activity] (0.5–4 Hz), a hallmark of SWS, promotes the global down-scaling of synapses that have become saturated during preceding periods of wakefulness and thus restores capacity for the encoding of new information.
After a night of wearing the eye mask, the participants received higher scores on the Psychomotor Vigilance Test, the most widely used test for alertness and attention. The researchers noted the importance of this finding, since staying alert is crucial for a variety of everyday tasks, such as driving, while educational benefits could also be achieved:7Sleep December 15, 2022
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.
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.
Sleep Masks Improve Sleep Quality
The featured study is unique in that it measured the effects of sleep masks on an ordinary night at home. However, it’s not the first to look at how sleep masks may influence sleep. A 2017 systematic review published in the Journal of Sleep Research analyzed the use of sleep masks for patients in an intensive care unit (ICU).8Journal of Sleep Research September 25, 2017
ICUs are filled with bright lights and noise, and sleep deprivation in ICU settings can lead to worse outcomes, including longer ICU stays and increased complication rates.9Journal of Sleep Research September 25, 2017 The study revealed that use of sleep masks, as well as ear plugs, by ICU patients significantly improved subjective sleep quality.
In another example, ICU patients who used a sleep mask and earplugs slept more hours and reported their quality of sleep significantly improved, compared to their own experience of not using a sleep mask in the ICU, as well as to other control group participants, who received routine care only.10International Journal of Nursing Practice May 14, 2019
Light Has a Significant Effect on Your Sleep-Wake Cycle
Humans have always been exposed to light from sunlight during the day and near-complete darkness at night, except for light from the moon, stars and fire. Now, light exposure at night is virtually inevitable, not only from cellphones, TVs, computers and artificial lighting indoors but also from streetlights and outdoor light pollution.
Light serves as the major synchronizer of your master body clock, which is composed of a group of cells in your brain called the suprachiasmatic nuclei. These nuclei synchronize to the light-dark cycle of your environment when certain wavelengths of light enter your eyes. As noted in the featured study:11Sleep December 15, 2022
In mammals, the sleep–wake cycle is regulated by the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. SCN activity is strongly synchronized by the light–dark cycle via intrinsically photosensitive retinal ganglion cells. The tight interaction between light and sleep regulation is, therefore, clear, with a large body of evidence supporting the impact of light on sleep timing, macro-architecture, and duration.
Not only does exposure to light at night affect your sleep quality, but it’s implicated in a number of chronic diseases. This is where simply wearing a sleep mask may be so beneficial, as simply closing your eyes isn’t enough. Even light that shines through closed eyelids can suppress melatonin,12BMC Res Notes. 2012; 5: 221 which can cause circadian disruptions that play a role in cancer.13Cancer February 8, 2021
It’s previously been shown that higher exposure to outdoor light at night may increase the risk of postmenopausal breast cancer,14International Journal of Cancer June 2, 2020 and evidence suggests light at night may increase thyroid cancer risk, too,15Cancer February 8, 2021 as thyroid function is regulated by circadian rhythm.
Health Risks of Light Exposure at Night
I’ve long stated that making a conscious effort to eliminate light in your bedroom — and if you can’t, wearing a sleep mask — can go a long way toward protecting your health. In March 2022, a study of 20 healthy young adults revealed that even one night of sleep with moderate light exposure increased nighttime heart rate, decreased heart rate variability and increased next-morning insulin resistance.16PNAS March 14, 2022
“These results demonstrate that a single night of exposure to room light during sleep can impair glucose homeostasis, potentially via increased SNS [sympathetic nervous system] activation,” the researchers noted.17PNAS March 14, 2022 A 2019 study, involving 43,722 women, also found that exposure to artificial light at night while sleeping was significantly associated with an increased risk of weight gain and obesity.18JAMA Internal Medicine June 10, 2019
In another study, exposure to any amount of light at night was linked to detrimental effects on the health of older adults, increasing the risk of obesity, high blood pressure and diabetes.19Sleep June 22, 2022 Compared to adults who were not exposed to light at night, those who did experience light exposure at night were significantly more likely to be obese or have high blood pressure or diabetes. Specifically:20Sleep June 22, 2022
- 40.7% of those exposed to LAN were obese, compared to 26.7% of those not exposed
- 17.8% of those exposed to LAN had diabetes, compared to 9.8% of those not exposed
- 73% of those exposed to LAN had high blood pressure, compared to 59.2% of those not exposed
Those exposed to light at night were also more likely to wake after falling asleep, and the researchers suggested more studies should be conducted to understand the long-term effects of light exposure at night on cardiometabolic risks.21Sleep June 22, 2022
Not Getting Enough REM Sleep Increases Risk of Death
Even during sleep, your body has a rhythm. It cycles through light sleep, non-REM (rapid eye movement), multiple additional sleep stages and REM sleep in 90- to 110-minute intervals. Ideally, this cycle will repeat four to six times a night.22The New York Times February 25, 2023
Each sleep stage is beneficial, but REM sleep, during which dreaming occurs, is being recognized as increasingly important — and it’s also affected by light. One study found that earlier exposure to light increased SWS “at the expense of” REM sleep.23Sleep December 15, 2022 During REM, your brain is as active as it is during wakefulness, but your body is paralyzed, which prevents you from acting out your dreams.
Hormonal changes and both memory reconsolidation and emotional processing occur during REM, which Matthew Walker, a professor of neuroscience and psychology at the University of California, Berkeley, told The New York Times is “like a form of overnight therapy.”24The New York Times February 25, 2023 Further, getting less REM sleep is linked to an increased risk of death. In a study of 4,050 people, a 13% increased risk of all-cause mortality was found over 12.1 years for every 5% reduction in REM sleep.25JAMA Neurol. 2020;77(10):1241-1251. doi: 10.1001/jamaneurol.2020.2108
You Can Harness Light and Darkness for Better Sleep
In the video above, Andrew Huberman, a neuroscientist and tenured professor in the department of neurobiology at Stanford University School of Medicine, details how to effectively harness light and darkness, as well as other factors, to fall asleep faster and stay asleep longer.
Huberman recommends viewing bright light, ideally from sunlight, within the first 30 to 60 minutes after waking to stimulate wakefulness throughout the day and help you fall asleep at night. Later in the day, there’s research showing that if you view light in the early evening hours, it may help mitigate some of the consequences of light exposure later in the evening.26Scientific Reports volume 9, Article number: 16064 (2019)
However, from around 6 p.m. or 7 p.m., into the hours when you get into bed and throughout the night while you’re asleep, it’s important to avoid bright artificial lights of any color.
Once the sun goes down, you should dim the lights in your environment and use as little artificial light as possible, including dimming your computer screen and avoiding overhead lights — opting for desk lamps instead. Better yet, use candlelight or moonlight after sunset.
If your bedroom is affected by light pollution, be sure to use blackout shades to keep light out and remove all sources of light from your bedroom, including a digital alarm clock or cellphone. You can also use a sleep mask for this purpose. Avoiding light at night will go a long way toward getting a great night’s sleep, but it’s not the only factor.
Toward that end, I’ve compiled 33 tips to optimize your sleep routine, which include not only paying attention to light and darkness, but also to sleep hygiene, temperature, lifestyle choices and more.
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This website is packed with information. There is so very much that I have learned here about the importance of quality sleep as it relates to our health. I had no knowledge of sleep affecting as much of our well-being as I have learned after reading this website. I prefer sleeping in total darkness. So much so that I put my entire head under the cover. I see that it is much better to wear a sleep mask. Are they comfortable? Melatonin is what helps us sleep properly, right? So, am I to understand that light reduces melatonin so we don’t sleep properly? There are pills that people take that have melatonin in them, Correct? The part about REM sleep and that we are paralyzed during that so we don’t act out our dreams amazed me. I have vivid dreams and can remember some of them the next day. If I am having dreams, does this mean that I am getting quality sleep? There is so much to learn about quality sleep on this site. I enjoyed the part that I experienced. Thank you for sharing your knowledge.
As someone who struggles with getting quality sleep, I must admit that this article on the benefits of using a sleep mask to be informative and helpful. It delves into the science behind how light exposure affects our circadian rhythms and sleep patterns, and how using a sleep mask can help mitigate the negative effects of light exposure, and that’s great.
It also covers some surprising benefits of using a sleep mask, such as reducing the appearance of wrinkles and improving skin health. As someone who values the importance of self-care, I found this aspect of the article particularly interesting.
Getting enough sleep is vital, but the quality of sleep is also very important. I have always found that light affects my sleep. Even as a child, I used to close my bedroom door to avoid the light that was left on for my siblings. But I have never really considered using a sleep mask.
After reading this, I will certainly get myself a sleep mask, as I am sure I will benefit from using one to get better quality sleep. Thank you for sharing this important health information.
I wandered upon this article trying to pick up some tips on ways to get a better sleep at night and I am thrilled having read this article!
Sleep masks are something that I have seen in television or in the movies but never really gave them a thought as a real option to aide me toward better sleep.
I had also never heard the theory of harnessing light and darkness for better sleep but in retrospect had put it into practice unknowingly yrs ago when I employed black out curtains in my bedroom to keep the sun outside while I was trying to sleep during the day because of work at night.
How much danger do you think is actually present from being deprived of REM sleep? This is a troubling assertion and I fear that yrs of inferior sleep may have put me in a bad position today.
Hey there, I stumbled upon this article while trying to find a solution for my sleepless nights, and boy was I surprised by what I learned! As someone who struggles with falling asleep, I never thought a sleep mask could be the answer to my problems.
Dr. Mercola, thank you for sharing these surprising health benefits of using a sleep mask. I had no idea that blocking out light while sleeping could not only help me sleep better but also boost my mood and even improve my skin! It’s like hitting two birds with one stone.
I appreciate how you explained the science behind the sleep mask and how it affects our circadian rhythm. I never realized how important it is to maintain a consistent sleep schedule, and the role that light plays in disrupting it.
I’m excited to give this a try and see how it improves my quality of sleep. I’ll definitely be recommending this article to my friends and family who also struggle with sleeping issues.
Once again, thank you, Dr. Mercola, for shedding light on this often-overlooked solution. Here’s to better sleep and better health!