We all have an internal clock that regulates our circadian rhythms, dictating when we sleep and wake. Light is the most significant factor in establishing our wakefulness during the day and sleepiness at night.
So, let me ask you: how dark is your bedroom? To understand why this matters and whether sleeping with an eye mask is beneficial, read on.
How is Light Related to Sleep?
Our circadian system evolved long before artificial light. Even a few watts can trick the brain into thinking it’s daytime. For example, using a tablet in bed is over 100 times brighter than being outside under a full moon, and working on a computer at night is about 10 times brighter than standing in a well-lit parking lot.
Light exposure at night disrupts the body’s natural sleep preparation processes. The pineal gland produces melatonin in response to darkness, a hormone crucial for regulating sleep.
What Happens When We Are Exposed to Light at Night?
Exposure to light at night suppresses melatonin production and alters sleep patterns. Adults who sleep with a night light experience shallower sleep and more frequent awakenings compared to those who sleep in darkness. Even outdoor artificial light, such as street lamps, can reduce sleep quality.
The impact of light at night extends beyond sleep. It’s linked to an increased risk of depressive symptoms, obesity, diabetes, and high blood pressure. Misaligned light exposure — dark during the day and light at night — is one reason shift work is associated with serious health problems.
Could Sleeping with an Eye Mask Help?
Researchers from Cardiff University in the UK conducted experiments to see if wearing an eye mask while sleeping could improve learning and alertness.
Around 90 healthy young adults, aged 18 to 35, alternated between sleeping with an eye mask and being exposed to light at night. They recorded their sleep patterns in a sleep diary.
In the first part of the study, participants wore an intact eye mask for a week. The following week, they wore an eye mask with holes exposing each eye, allowing light to pass through.
After sleeping with no light exposure (wearing the intact eye mask) and minimal light exposure (the eye mask with holes), participants completed three cognitive tasks on days six and seven of each week:
- Paired-Associate Learning Task: This task measures how effectively a person learns new associations, such as related word pairs. Participants performed better after wearing an intact eye mask compared to light exposure at night.
- Psychomotor Vigilance Test: This test assesses alertness. Blocking light at night improved reaction times.
- Motor Skill Learning Test: This involved tapping a five-digit sequence in the correct order. There was no performance difference whether participants wore an intact eye mask or were exposed to light at night.
What Else Did the Researchers Learn?
No research study is perfect, so take these conclusions with a grain of salt.
According to sleep diary data, there was no difference in the amount of sleep or perceptions of sleep quality, regardless of eye mask use.
In a second experiment with about 30 participants, researchers used the Dreem headband to monitor sleep objectively. They found no changes in sleep structure, such as REM sleep duration, when wearing an eye mask.
Should You Rush Out to Buy an Eye Mask Before an Important Meeting or Exam?
If you decide to try an eye mask, there’s no need to pay for overnight shipping. Instead, follow this rule of thumb: “bright days, dark nights.”
- Daytime: Get as much natural daylight as possible. Pick up your morning bagel from a local bakery, take a short walk during your afternoon break.
- Evening: Reduce exposure to electronic devices, and use night-dimming modes. Turn off unnecessary lights and make your bedroom as dark as possible when you go to bed. Turn the alarm clock away from you or cover the light on a humidifier.
Of course, a comfortable eye mask might be a valuable addition to your light hygiene toolkit. Most cost $10 to $20, potentially improving your sleep and cognitive performance for the price of a few cups of coffee.