What’s the big deal about exposure to screens and sleep?
Does it really matter? What is it about screens that causes problems with sleep? Is it the stimulation of what we are doing on our devices or something about the light from screens? Checking email or social media for the last time just before going to sleep can have a stimulating effect and make it harder to switch off, but it may be that light from the device in the hours before sleep has an even bigger effect.
What is the impact of screens on sleep?
The main impact of screens particularly when used just before going to sleep is from blue wavelength light. Research over the last 25 years has shown that light at a wavelength of 459-485 nanometers, which is a blue-green colour, is detected by photosensitive retinal ganglion cells in the retina. These cells then pass a signal to the brain that suppresses the increase in melatonin production that naturally occurs after the sun goes down. To get to sleep we need melatonin levels to gradually rise as this helps to control the sleep-wake regulation and start the shutting-down process. However, if we are exposed to light of a blue wavelength prior to sleep it delays this process and makes it harder to switch off. It can also push our body clocks to a later time, making it harder to wake up in the morning.
We have been exposed to varying lights after the sun has gone down since the discovery of fire. Prior to electrical light in the 19th century, although we had light from candles or flames, it did not seem to have as much of an effect on sleep. The light from flames is warmer, mainly yellow or orange wavelengths and doesn’t have the same effect on melatonin production as colder, blue wavelength light.
Then in the 20th century, in addition to electrical light, we had television screens in our bedroom. However, televisions were quite a long way from our eye, and as the intensity of light is inversely proportional to the square of distance of the light source from the eye, they only had a modest effect on sleep. But in the 21st century, with screens such as smartphones, tablets and laptops in the bed with us, close to our eyes, light from screens has the potential to significantly impact on our sleep. Even if the screens are relatively small, because of the relationship between the intensity of light and distance from the source, the intensity of light from a screen held in our hand in bed can be much more than from a television at the foot of the bed.
There is also a role of what we are doing on our screens impacting on our ability to sleep. If what we are doing is engaging and activating such as work-related activities like emails, or emotional content such as what our friends are doing on social media it can make it much harder to switch off.
What can be done to reduce the effect of light from screens?
The ideal way to avoid the impact of light from screens is to not have screens emitting blue light close to us in the bedroom or in the evening before going to bed. However, in our modern world that is often unrealistic as screens and our devices are our way of communicating with friends and family, and we can get a sense of feeling left out without that form of communication. An alternative is to reduce the intensity of blue light from screens. This can be done on mobile devices using apps or settings within the operating system.
- iOS: 9.3 and later have the Night Shift function built in. This function takes the blue light out of the screen after a set time giving the screen a warmer, orange shade that has less impact on melatonin levels. See this link for instructions on how to activate Night Shift
- Android: The f.lux app can be used on Android devices to reduce blue wavelength light and like the Night Shift function in iOS can be set to come on automatically at particular times. You can also set an alarm within the f.lux app to prompt you to begin getting ready for bed and remind you to turn off activating activities or programs on your device.
- Laptop or desktop computers: The f.lux app is also available for desktop computers running Windows or Mac OS.
- Orange-tinted glasses: An alternative to changing the light from the device is to put a filter between the device and your retina. This can be done using glasses with an orange tint that effectively filter out blue wavelength light and reduce the amount of blue wavelength light reaching the back of the eye. Examples of these are Uvex glasses.
- Smart lighting: With increasing recognition of the impact on light on sleep and health, companies are beginning to produce lights for houses and workplaces that are capable of changing wavelength at different times through the day, and can be adjusted from a smartphone app. The globes can be set to produce colder, blue colours in the morning and warmer, yellow-orange colours at night. One example of this technology are the C-Sleep globes from GE.
Who should be particularly careful about light from screens?
There are a number of groups who should be particularly careful about exposure to blue wavelength light from screens after the sun goes down:
- Teenagers and adolescents: are particularly susceptible to the effects of light from screens prior to retiring to bed. They are at a time in their life when their body clock tends to want to run at a later time already making it harder for them to get off to sleep and harder to get up in the morning. Anything that will exacerbate this, such as blue wavelength light in the evening, will increase their tendency to phase delay.
The tendency of teenagers and adolescents to sleep at progressively later times is discussed in more detail in the post – Can’t get your teenager our of bed.
- People with sleep difficulties or insomnia: who are struggling with switching off at night and getting to sleep or waking during the night should be particularly careful about blue wavelength light prior to retiring to bed. It can impact not just on getting to sleep but can also result in people being more prone to awakening during the night.
- People with depression or bipolar disorder: can have a tendency to circadian phase delay, or sleeping later and later, much like adolescents. The exact relationship is not clear, but a subset of people with depression or bipolar disorder are sensitive to the effects of light, and find that evening light adds to difficulties with sleep that are already common in depression.
What about light in the morning?
Whilst exposure to blue wavelength light in the evening can have a negative impact on sleep, in the morning it has a positive impact. Morning light helps to regulate sleep and wake rhythms and can help people feel less tired both in the morning and throughout the day. There is also research supporting the use of morning light to help manage jet-lag, insomnia and depression, particularly seasonal depression.
For more information on morning light therapy see this post.
Related posts & links:
- Can’t get your teenager out of bed?
- Light therapy – What are the options?
- Managing the circadian rhythm – Video
- Electronics in the bedroom – National Sleep Foundation
- Bright screens could delay bedtime – Scientific American
- Bright screens at night imperil sleep of young teens – Brown University
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