In recent years, young people who sleep less than eight hours have increased. This event seems to be multifactorial but electronic devices have special importance. Twenty five years ago, nobody would have imagined people using electronic devices in bedrooms at night. Noadays we are seeing some consequences of this habit.
Technology always brings social changes
Currently, it is very common to go to sleep with TVs, mobile phones, tablets, computers, videogames consoles, etc. An important aspect of the relationship between young people and screens is the use of electronic devices at night and therefore, a new problem: It might delay sleeping times or even reduce the total sleep time. The insuficient or poor quality of sleep can be explained in three different ways:
Sleep time displacement: More time on screen means less time to sleep.
Social: Social interaction can hinder the abillity to fall asleep.
The light effect on the circadian rhythm: this is the object of this article, let's discuss it.
Light, melatonin and circadian rhythm
The central circadian circle can be summarized in three components:
Input pathways: Provides "signals" to synchronize the endogenous central clock to the external environment.
The central clock: Which generates the circadian circle's rythms
Output pathways: that convey the signals of the central clock to the other regulatory systems in the brain and body.
Light is absorbed by photopigments in the retina. One of those pigments is melanopsin, that is located in very specialiced cells in the retine. Melanopsine absorbes low length wave light better, like the blue light. Therefore, blue light stimulus can generate greater stimulus. But in practice, that diference could be insignificant.
The hypothalamus processes the information received from the retinian cells and sends a response to the pineal gland. That's where the melatonine is synthetized and released. Melatonin is a natural sleep inductor, and its release can be suppressed by the light stimulus.
What happends during the night?
The effect of the light on our body has been widely studied. The light stimulus can affect our alert status. In fact, it is known that an iPad at maximum brightness during 2 hours can suppress melatonin significatively. Nevertheless, the effect of white light color temperature is still unclear.
In sum, there is an association between screen time use and sleep disorders. More than thinking about the blue light, we should turn off all our electronic devices before going to sleep.
Tips for nocturnal "screen lovers"
There are some 'tips' that you can follow to reduce light exposure if you can't turn off your devices:
Decrease the brightness to the minimum.
Use applications to filter blue light at night.
Set the "dark mode" to reduce the emitted light.
But, the best but least popular tip, it's simply avoid using electronic devices before sleep.
The use of electronic devices is associated with poor quality sleep. The light of screens before going to sleep could reduce the melatonin level and delay sleep time. Blue light could be a more powerful stimulus for melatonin supression, but the evidence is insufficient to affirm it.
Wood B, Rea MS, Plitnick B, Figueiro MG. Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression. Appl Ergon 2013;44(2):237e40.
Knufinke M, Fittkau-Koch L, Most E, Kompier M, Nieuwenhuys A. Restricting short-wavelength light in the evening to improve sleep in recreational athletes - A pilot study. Eur J Sport Sci. 2019 Jul;19(6):728-735.
Hale L, Guan S, Screen time and sleep among school-aged children and adolescents: A systematic literature review, Sleep Medicine Reviews (2014), http://dx.doi.org/10.1016/j.smrv.2014.07.007
Ingrid Nesdal Fossum, Linn Tinnesand Nordnes, Sunniva Straume Storemark, Bjorn Bjorvatn & Stale Pallesen, Behavioral Sleep Medicine (2013): The Association Between Use of Electronic Media in Bed Before Going to Sleep and Insomnia Symptoms, Daytime Sleepiness, Morningness, and Chronotype, Behavioral Sleep Medicine, DOI: 10.1080/15402002.2013.819468
John W. Winkelman. Insomnia Disorder N Engl J Med 2015;373:1437-44. DOI: 10.1056/NEJMcp1412740
Gianluca Tosini, Ian Ferguson, Kazuo Tsubota. Effects of blue light on the circadian system and eye physiology. Molecular Vision 2016; 22:61-72