How Does Screen Light Affect Sleep?

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 lightat 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.

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.

All life on Earth has developed patterns ofactivity 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 over 24 hours in length.However, light profoundly affects the timing of sleep and wakefulness,metabolism, and hormone release.

Morning sunlight has a key influence onlife's functions. It promotes wakefulness and ends sleep. It can help shift thedesire for sleep slightly earlier. In the winter, when sunlight comes later, wemay want to sleep in or suffer from symptoms called winter depression.

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 togo to bed and wake later. Have you ever noticed how easy it is to stay upanother 15 minutes but how difficult it is to wake just 15 minutes earlier?Morning sunlight can profoundly reset this internal clock.

Unfortunately, artificial light at night can negatively affect the timing of our sleep. Light shifts sleep timing, and light at night can shift our desire for sleep later. This can result indifficulty 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 orpoor sleep quality, you are unlikely to be impacted.

There are several important factors toconsider:

1. The Source of Light

Artificial light can come from light bulb sand many other sources, including the screens of televisions, computers,tablets, smartphones, e-books, and even wearable tech. Each of these can generate a different intensity of light. Near screens may have more impact than those across a room.

2. The Amount of Light

Most overhead lights generate a light intensity that varies from about 500 to several thousand lux. For comparison,full sunlight at midday may be 100,000 lux in intensity. Commercially available light boxes often generate about 10,000 lux. The screen of your smartphone may create hundreds of lux of light, depending on the settings you use. Even smaller amounts of light, such as from a screen, may have an impact in some people.

3. The Color of Light

Much is made of the fact that blue light is responsible for shifting circadian rhythms. Full spectrum light - what you might consider as "white light" or "natural light" - contains the blue wave lengths as well. Blue-blocker sunglasses (with an amber or orange lens) and screen filters are sold to block this light wave length.

4. The Timing of Light

One of the most important variables is when you are exposed to light, including from artificial sources. There is evidence that light at night could shift your desire for sleep by about 1 hour. This delays your ability to fall asleep and may impact your desire to wake in the morning.

Therefore, it is very important to turn down the lights at night, especially preceding your bedtime. 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 some music, read a book printed on old-fashioned paper, or page through a magazine. By reducing and eliminating your exposure to light atnight, you may find that you are able to sleep better. If you continue to struggle, speak with a sleep doctor about additional treatment options.

Source: Kryger, MH et al. "Principlesand Practice of Sleep Medicine." Elsevier, 5th edition. 2011.