Mobile devices ruin sleep 27.12.2014

The biological clock depends on the natural cycle of day and night, but scientific and technological progress has brought us artificial lighting, so that we are no longer dependent on sunlight, and can work, read and generally be active at night too. At the same time, many molecular, cellular, physiological and mental processes depend on daily rhythms. And what then happens to us when our watch sees light around, while, according to the natural course of things, there should already be darkness around?

Recently, this issue has been studied in the most intent way, and the results are disappointing. Numerous scientific papers show that a disturbed circadian rhythm affects not only higher nervous activity, but also, for example, metabolism: going to bed at the wrong time or regularly not getting enough sleep, you risk developing diabetes, overweight problems, etc. Moreover, sometimes you don’t even need to break the daily rhythm itself, just abnormally bright lighting at an inopportune time is enough.

Two years ago, employees of Johns Hopkins University (USA) published an article in Nature stating that even if you go to bed at the right time, the bright lighting that accompanies us to the last can still cause harm in itself. Animals that were forced to live constantly in bright light showed signs of depression: they ceased to be interested in others, their memory deteriorated and the level of stress hormones increased. The authors of the work suggested that the depression of a modern urban person may be due to the fact that in cities at night it is "light as day".

However, two objections can immediately be raised here. Firstly, the results of some studies still need to be rechecked on humans, after all, our physiology differs from the physiology of laboratory mice, which in nature should generally lead a nocturnal lifestyle. Secondly, many people read something from the screens of laptops, smartphones, tablets, etc. before going to bed, but at the same time turn off the overhead light, remaining in almost complete darkness. Can the radiation from the screen of a mobile device affect our circadian rhythm that much?

It turns out it can. Anna-Maria Chang (Anne-Marie Chang) and her colleagues from Boston's Brigham and Women's Hospital at Harvard University (USA) observed twelve adults who regularly read a book before going to bed for two weeks. Only some read it for five days, first on paper, and then on an electronic "reader", while others did the opposite - they started with an electronic device and continued with a paper-printed version. As for the content, it could be anything, but it had to be just leisure reading, in addition, images and puzzles were excluded. Time was allotted for reading from 18-00 to 22-00, for sleep - from 22-00 to 6-00.

Electronic "readers" were also not all. The researchers measured the amount of light emitted from various mobile devices, including the iPad, iPhone, Kindle, Kindle Fire, and Nook Color. The Kindle devices did not emit light, but the iPad, Kindle Fire and Nook Color shone about the same, although the iPad was brighter than the others. So the experiment was set with the iPad.

It turned out that those who read from electronic devices fell asleep 10 minutes longer and their REM sleep phase decreased. In addition, they felt more tired the next morning and took longer to wake up. When reading from the screen, the level of the hormone melatonin, which controls the biological clock, decreased in the blood. In the evening, before going to bed, it should increase (it is because of him, by the way, that we feel sleepy), but here everything happened the other way around. According to the authors of the work, the reason for this effect from electronic devices is that their radiation is enriched with blue light, according to which the biological clock in the brain is oriented.

So this is another argument in favor of surfing the Internet less and reading more paper books - at least in the evenings. Well, or at least carefully choose another electronic toy.