How Blue Light Affects Sleep

Young woman uses smartphone in bed at night

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From the time we wake up each morning to when we go to bed at night, we may not think much about the light we observe each day. We turn the lights in our homes on and off as we use them, let sunlight into the room on sunny days, and we are constantly exposed to the light from digital screens, whether from our smartphones, TVs, or computers.

I always tell my patients that light is medicine, and that you need to consume the right kinds of light to keep yourself at your best. Sunlight is the best source of Vitamin D you can get, and exposure to blue light or white light during the day can have positive effects on your mood and your alertness. However, too much of anything can be bad, and that goes for light exposure as well.

Because of our favorite electronic devices, blue light is a nearly constant presence in our lives, but too much can actually cause poor sleep, among other issues. Before we dive into how blue light can affect your sleep, let’s take a look at the different colors of light that exist.

What are the Different Colors of Light?

Light itself is made up of electromagnetic radiation, creating a form of energy. Each light wavelength comes in different “colors” based on the type of energy contained within. Some of the colors on the visible light spectrum include:

  • White Light, which is a combination of all light colors
  • Red Light
  • Yellow or Orange Light
  • Blue Light

Visible light is only a small part of what is created by the electromagnetic spectrum— all of these colors are visible in the rainbow. Blue light is only a portion of this visible spectrum, but it plays a key part in how we function each day.

Light is the most important environmental factor in determining your sleep-wake cycle and how your circadian rhythm will function, and until the invention of artificial light and electronic devices, our circadian rhythms were influenced primarily by the sun. So with all this in mind, let’s take a look at the effect blue light can have on your sleep.

How Can Blue Light Harm Sleep?

Sleep disturbances occur when the circadian rhythm is disrupted by human activity such as being exposed to artificial light or bright light. Exposure to blue light as well as white light too soon before bed can lead to sleep disturbances.

But let’s get one thing out of the way: blue light is not inherently bad. I mentioned above that blue light and white light exposure during the day is good for your health and wellbeing— but overexposure, especially at night, can have a negative effect on your circadian rhythm and your sleep cycle. Alternatively, red, yellow, or orange light have little to no effect on your circadian rhythm, and these light colors are safe to use at night.

Too much blue light exposure before bedtime can inhibit the production of melatonin, the “sleep” hormone produced in your pineal gland that regulates your circadian rhythm. Blue light exposure can lead to inadequate melatonin production, which can hinder your ability to fall or stay asleep.

It doesn’t take much blue light to make an impact on your rest either. Harvard sleep researcher Stephen Lockley has noted that a level of brightness exceeded by most table lamps and all nightlights can have an effect on your sleep cycle, and adds that nighttime light exposure is a key cause of sleep deprivation.

The main light source causing problems at night is the artificial blue light generated by a number of electronic devices in our homes.

What Devices Produce Blue Light?

While our favorite devices are convenient and have likely become integral to our everyday lives, they may also be sabotaging your sleep by producing artificial blue light and inhibiting your body’s ability to produce melatonin. Some of these devices include:

  • Cell Phones
  • Computer Screens
  • Tablets
  • Televisions

Other light sources, such as LED lights or fluorescent lighting, also produce artificial blue light that can hinder your body’s melatonin production. It seems that nowadays blue light really is everywhere, so what can you do to ensure you can get a good night’s sleep each night?

How to Manage Blue Light for Better Sleep

It’s important to be aware of how much time you spend exposed to blue light each day, whether it’s from the lights in your home or place of employment, or from the electronic devices you use throughout the day.

Ideally, you want to stop using your electronic devices at least 90 minutes before bedtime each night. If you do your Power Down Hour each night (which starts 60 min before bed), create a specific cut-off point for device usage (like the beginning). Sometimes that may not be enough though. Thankfully, there are ways to reduce your exposure to blue light at night, even if you’re using your electronic devices.

I always wear blue light blocking glasses at night, and I highly recommend them! These help block artificial blue light from your devices, as well as from artificial lighting wherever you go. They won’t hinder your vision, and using them is more effective than using night mode or screen filters alone. The Amber color is critical for effectiveness. For more information, check out my article about things to know before you buy blue light blocking glasses.

If you enjoy reading in bed, try using a light source that emits red or orange light, rather than blue. There are speciality bulbs you can install, or just use a directional book light. If you live in an area where there is a lot of bothersome ambient light, an eye mask or blackout curtains are excellent ways to block out that light and get a good night’s rest.

You may be wondering why I’m not suggesting using “night mode,”or the many blue light filtering apps available. Put simply, they just don’t work. These apps are a good idea in theory, but they’re not effective at blocking blue light or increasing melatonin production. A 2018 study found that Apple’s Night Shift app was ineffective in reversing melatonin suppression created by using our devices at night.

Just remember, light is medicine. We need light to keep us feeling our best and functioning properly, but we also need to manage our light exposure to make sure we don’t sabotage our sleep. This is especially true for blue light— during the day, blue light exposure is beneficial to our focus and alertness, but too much of it at night can disrupt your sleep cycle.

It’s true that our devices, especially our phones, have become very important and constant parts of our day-to-day lives. However, it’s important to use them in moderation at night to ensure that you get the good night’s sleep you need. Sometimes it’s hard to be mindful of how much blue light we’re exposed to each day, but a little extra mindfulness can go a long way in making sure we sleep well at night.

Sweet Dreams,

Michael J. Breus, PhD, FAASM

The Sleep Doctor

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Michael Breus, Ph.D - The Sleep Doctor is a Diplomate of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine and one of only 168 psychologists to pass the Sleep Medical Specialty Board without going to medical school. Dr. Breus is a sought after lecturer and his knowledge is shared daily in major national media worldwide including Today, Dr. Oz, Oprah, and for fourteen years as the sleep expert on WebMD. Dr. Breus is the bestselling author of The Power of When, The Sleep Doctor’s Diet Plan and Good Night!

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