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Ever wonder what’s lurking in the darkness while you sleep? Better sleep, of course! The real Boogeyman (bad moods, health complications, more accidents) comes when you sleep with too much light in your bedroom.

It’s pretty well established: Sleeping with the lights on isn’t good for humans.

Research indicates sleeping with the lights on causes lighter sleep (excuse the pun), more frequent waking, and impacts brain activity! Read on for more details about why darkness is best for rest.

Imagine how black nighttime was before the invention of artificial light? If the sun were down by 7 p.m., you could go to bed or fiddle around by fire light.

Once a month you could bask in the glow of the full moon, for a treat. Now, your home might be lit up like daytime 24 hours a day. Well, friend, there are consequences for all that illumination.

A 2016 study of artificial outdoor lights showed the following impacts on sleep behavior. People who lived where there was more artificial outdoor nighttime light:

  • went to bed later
  • woke up later
  • slept less
  • were more sleepy during the day
  • were less satisfied with the duration and quality of their sleep

If so much sleep trouble is tied to outdoor lights, imagine the impact of bright light bulbs and light-emitting devices aimed directly at your face!

Something as innocent as reading an e-book before bed may also mean it takes more time to fall asleep, suppressed melatonin production, reduced and delayed REM sleep, and less alertness the next morning.

If your sleep cycle is “off,” what does that mean for overall health? Check this out…

Odd bedfellows: Sleep and weight

People who sleep less than 6 hours per day are more likely to have larger bodies. Weight gain is linked to obstructive sleep apnea, insufficient sleep syndrome, and narcolepsy.

Scientists believe this is because a healthy sleep cycle is necessary for the body to use energy properly and produce ideal levels of hormones that impact weight regulation.

Not getting enough sleep can also cause you to eat more during the day (like chasing a burst of energy from hearty foods to make up for your missed Zzz’s.)

Being up late will get you down

The relationship between sleep and depression is actually a two-way street — depression causes poor sleep and not sleeping well can exacerbate depression.

Researchers say people with depression experience problems with both REM and non-REM sleep and sleep continuity. Taking antidepressants also seems to disrupt REM sleep.

Sleep electroencephalograms may prove useful in diagnosing and evaluating therapies for depression.

Good sleep for safety first

Sleeping less than recommended (7 to 9 hours per night for adults) makes you less alert during the day. Slow thinking and slow reaction times lead to more accidents while driving and performing other physical tasks.

Not sleeping means serious health risks

Who probably has the most trouble sleeping in complete darkness? People who work shifts and have to sleep during daytime hours.

Studies have shown a link between shift work and chronic illnesses like type 2 diabetes, coronary heart disease, stroke, and cancer.

Scientists who reviewed literature on these subjects found shift work and insufficient sleep had similar impacts on risk for cardiometabolic diseases and accidents.

  • A quick nap. If you want to take a very light nap for an energy boost, leaving the lights on may help you avoid slipping into an afternoon coma that lasts for hours and leaves you wondering what day it is.
  • Scared little ones. For children who are afraid of the dark, a small night-light may do less harm than delayed bedtimes and anxiety. Have a plan to phase out the extra light or try a night-light that fades after your child falls asleep.
  • Older adults. Older people who have diminished vision or physical dexterity may prefer to have a light to ease their fear of falling when they get up during the night.

Light travels through your eyes to the hypothalamus inside your brain. Inside the hypothalamus is the suprachiasmatic nucleus (so cool, right?!) which interprets light exposure to regulate your circadian rhythms. Circadian rhythms are responsible for sleeping, wakefulness, body temperature, metabolism, and release of hormones.

The pineal gland produces the hormone melatonin based on info it receives from the suprachiasmatic nucleus.

If your eyes are flooded with light before bedtime, you don’t produce enough melatonin to help you fall asleep and sleep well. That’s why it’s so important to sync our indoor environments to the natural light and dark rhythm of the sun rising and setting.

Once you fall asleep, too much light can still impact your ability to achieve REM sleep and other sleep stages. All sleep stages are important for your brain and body.

Why should you even care about sleeping well? Here are just a few ways good sleep makes life better:

  • healthy metabolism
  • better immune function
  • improved ability to learn and retain memories
  • better physical performance
  • improved cardiovascular health
  • less risk for depression
  • lower inflammation

Most light bulbs mimic natural light and trick your brain into staying awake. Red lights, on the other hand, don’t seem to have the same stimulating effect. Try them in your bedroom or in night-lights.

If you can’t control the lighting, at least add some of these healthy recommendations to your sleep routine:

  • Stick to a schedule, going to bed and waking up at the same time every day.
  • Exercise 20 to 30 minutes a day (at least a few hours before bedtime).
  • Avoid caffeine, nicotine, and alcohol before bed.
  • Do something relaxing before bed like reading or taking a bath.
  • Reduce as much light and sound in your sleep environment as possible.
  • Keep the room at a comfortable temperature.
  • Avoid watching TV or using a computer in bed.
  • If you can’t fall asleep, get up and do something, then try to lie down again.

These tips can help you engage your natural sleep/wake cycle:

  • Get some light during the day — either through sun exposure or an artificial light box that simulates the sun.
  • Try light-blocking curtains or a sleep mask and keep lights dim if you wake up during the night.
  • If you work at night and sleep during the day, try dark sunglasses as soon as your shift ends to signal to the brain that you’re ready for sleep.

Your brain needs exposure to a natural cycle of darkness and light to induce ideal sleep duration and quality.

If you live in a brightly lit environment before bedtime, melatonin is suppressed and your sleep suffers. You may also be more vulnerable to accidents, depression, and chronic diseases.

Hack your sleep superpower by adopting good sleep habits and keeping the bedroom as dark as possible.