We often complain about people around us constantly being glued to their phone. Mobile technology is everywhere these days. When not on the go, we still tend to stare at computer screens both in the office and back at home. For many, this addiction to high-tech devices represents a way to be connected to friends and family. Many others think that these devices isolate us from real interaction with the world around us. One way or another, we do indeed spend too much time with our computers, laptops, tablets, and smartphones.

Apart from changing the way we communicate (for better or worse), all these devices have one more thing in common: bright screens. These light emitting screens can seriously affect our sleeping pattern. Moreover, the blue light (of a wavelength of ~470 nm) that is emitted by these devices is particularly harmful to normal sleep.

These days, an increasingly large number of people report problems with sleeping. Many people can’t fall asleep in the evening and then do not feel refreshed the next morning when they have to go to work. Lots of people complain about disturbed shallow sleeping and frequent awakenings at night. With normal sleeping hours often affected, people sleep less at night and if they can, compensate for this lack of sleep with daytime naps.

Disturbed sleep patterns are often linked to a diminished ability to focus on work, lack of motivation, and a generally low mood. This may lead to conflicts and stress at the workplace resulting, in some cases, in anxiety and depression. There are long-term negative consequences for other organs and systems of the body too. For instance, the link between chronically bad sleep and cardiovascular problems is well documented. Sleeping pattern disturbances also contribute to excessive body weight. It is estimated that around half of all Americans suffer from chronic stress at moderate or severe levels. Disturbingly, this number is growing in recent years.

Apart from many social and psychological factors, the growing level of stress in the general population can also be linked to the growing and excessive use of computers and smartphones. Exposure to bright screens in the evening hours is particularly harmful.

Our circadian rhythm (the sleep-wake pattern) is regulated by our exposure to light. There are several components of this system that are particularly important. First, we have specific cells in our eye retina that function as detectors of the duration and intensity of light. These cells, called intrinsically photosensitive retinal ganglion cells (ipRGCs), are particularly sensitive to short wavelength blue light.

Light-exposed ipRGC cells send signals to the suprachiasmatic nucleus in the brain. This region is responsible for setting the body clock, achieved by regulating the production of the hormone melatonin in the pineal gland. Melatonin plays a role in the adjusting mechanism: it synchronizes the body’s circadian rhythms with the real-life cycle of day and night experienced by the body. The problem is, this system can be easily fooled by prolonged exposure to artificial light. When you stare at your laptop screen late in the evening, you are also sending a signal to your brain that you are currently experiencing daytime. Your body will try to adjust accordingly to help you take advantage of daytime hours—it will reduce your desire to sleep. And once the screen is off, you don’t feel like sleeping anymore…

Recently published experimental data demonstrated that just two hours of evening exposure to bright computer screens emitting blue light decreases sleep duration and, more importantly, dramatically reduces its quality. People exposed to computer screens were awakening during the night much more often compared to those who did not use computers in the evening. The data also demonstrated that both the type of light emitted by the screens and its intensity is important for nighttime sleep quality. The screens with low brightness were less disturbing for sleep quality, and the screens emitting red light did not affect nighttime sleep at all.

Exposure to blue light-emitting bright screens in the morning is actually a positive thing: it can help to readjust the body to the correct time of the day. In fact, morning exposure to blue light is even used in a number of bright light therapy methods aimed at normalizing the circadian cycle, particularly in elderly people who often experience sleep-wake pattern disturbances.

It is quite unlikely that after reading this article anyone will immediately give up the habit of late-night internet browsing or chatting with friends via social networks before going to sleep. There are, however, several simple methods to reduce evening exposure to blue light emitted by screens. First, you can reduce the brightness of your screen. You can also change the background color while reading some types of documents. Text with white letters on a black background definitely reduces light exposure. If you anticipate working with documents in the evening, it might be a good idea to print them out. Paper is certainly much friendlier to the eyes. It is also possible to cover your computer screens with special filters that block out blue light. These small changes won’t require any major changes to your habits and routine but will help you to regain a normal sleep-wake pattern and bolster feeling refreshed the next day.

References

Arendt J. (2006) Melatonin and human rhythms. Chronobiol Int. 23(1-2): 21-37. DOI: 10.1080/07420520500464361.

Figueiro, M.G., Wood, B., Plitnick, B. et al. (2011) The impact of light from computer monitors on melatonin levels in college students. Neuro Endocrinol Lett. 32(2):158-63. PMID: 21552190.

Skene DJ, Arendt J. (2006) Human circadian rhythms: physiological and therapeutic relevance of light and melatonin. Ann Clin Biochem. 43(Pt 5): 344-53. DOI: 10.1258/000456306778520142.

Wright HR, Lack LC, Kennaway DJ. (2004) Differential effects of light wavelength in phase advancing the melatonin rhythm. J Pineal Res. 36(2): 140-4. DOI: 10.1046/j.1600-079X.2003.00108.x.

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