How Screen Light From Devices Affects Your Sleep

Artificial light may impact circadian rhythms and lead to insomnia

In a world increasingly dependent on technology, bright screens are more commonly part of our everyday life. These screens range broadly in size and purpose: televisions, computers, tablets, smartphones, e-books, and even wearable tech.

How does this artificial light, especially when viewed at night, potentially impact our sleep? Learn how light at night affects our body’s circadian rhythm and whether it might contribute to insomnia and difficulty awakening. In addition, consider ways to reduce light exposure and counteract its effects.

A woman texting on her bed at night
Yiu Yu Hoi / Getty Images

How Modern Technology Changed Life and Sleep

It is hard to imagine a time before artificial light existed. It is such an integral part of our lives that we consider ourselves deeply inconvenienced when we lose power in a storm. Think back to what life was like before modern technology, such as computers and televisions, before light bulbs, and even before electricity.

Primitive societies and people were highly dependent on the natural availability of light. The sun ruled life. It is no surprise that it was worshiped in ancient Egypt. When artificial light became possible, things dramatically changed.

The Influence of Light on the Body’s Functions

All life on Earth has developed patterns of activity dependent on the timing of day and night. When isolated from the natural environment, innate circadian patterns will be revealed. As an example, most humans have an internal clock that runs just about 24 hours in length (24 hours and 11 minutes, plus or minus 16 minutes, to be exact). However, exposure to light resets our clock, and profoundly affects the timing of sleep and wakefulness, metabolism (e.g. insulin/glucose), and hormone (e.g. melatonin, cortisol) release.

Due to the length of our internal clock, our bodies have a natural tendency towards delay in the timing of our sleep. This means that we always find it easier to go to bed later and wake later. Have you ever noticed how easy it is to stay up another 15 minutes but how difficult it is to wake just 15 minutes earlier?

Morning sunlight has a key influence on life’s functions. The composition of morning light resets our internal clock and promotes wakefulness and ends sleep. It can help shift the desire for sleep slightly earlier in the evening. In the winter, when sunlight comes later, we may want to sleep in, or suffer from symptoms called winter depression.

How Artificial Light at Night Impacts Sleep

Artifical light can also impact our circadian rhythm. Unfortunately, artificial light at night can negatively affect the timing of our sleep, and can shift our desire for sleep later into the evening. This can result in difficulty falling asleep, as occurs with insomnia. Night owls, or those with delayed sleep phase syndrome, may be especially susceptible.

Not everyone is sensitive to these effects. If you are especially sleepy, perhaps due to inadequate total sleep time or poor sleep quality, you are unlikely to be impacted.

There are several important factors to consider:

  • The Source of Light: Artificial light can come from light bulbs and many other sources, including the screens of televisions, computers, tablets, smartphones, e-books, and even wearable tech. Each of these can generate different amounts of light that can impact our sleep.
  • The Amount of Light: Each source of light generates its own light intensity. For comparison, full sunlight at midday may be 100,000 lux, whereas commercially available light boxes that are used to treat seasonal affective disorder often generate about 10,000 lux, and the screen of your smartphone may create hundreds of lux of light intensity, depending on the settings you use. (A unit of lux describes how much light falls on a certain area; whereas a unit of lumens tells you the total amount of light emitted by the light source). Using lux helps us understand how nearby screens may have more impact on us than the same screen from across a room. Even smaller amounts of light, such as from a smart phone that is held 12 inches from our face before going to sleep, may have a negative impact on our sleep.
  • The Color of Light​​​​: Much is made of the fact that blue light is responsible for shifting circadian rhythms, while red, yellow, and orange light waves do not have this effect. Full-spectrum light, what you might consider as “white light” or “natural light,” contains the blue wavelengths as well. Digital screen filters, blue light blocking glasses, and prescription glasses with FL-41 tint are sold to block this blue light wavelength to minimize disruption to our circadian rhythms.
  • The Timing of Light: One of the most important variables is when you are exposed to light, including from natural and artificial sources. There is evidence that exposure to light at night could shift your desire for sleep by about 90 minutes. This delays your ability to fall asleep and may impact your desire to wake in the morning.

Tips for Getting Better Sleep

Therefore, it is very important to turn down the lights at night, especially preceding your bedtime. Ideally, light at night should be dim (~3 lux), containing red, yellow, or orange wavelengths, and efforts should be made to block blue light from devices. Some people may need to avoid excessive artificial light exposure for the 1-2 hours before going to bed. This means turning off the phone, powering down the computer, and avoiding light from tablets, e-books, and other sources.

Instead, try to stick to low-tech options. Listen to relaxing music, sip a warm cup of tea, or try meditation. By reducing and eliminating your exposure to light at night, you may find that you are able to sleep better. If you continue to struggle, speak with a sleep doctor about additional treatment options.

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13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. Sixth edition. Elsevier; 2017.