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Photo Source: Pixabay checking his cell phone before going to bed may not do so much harm to the eyes, but the damage to the body is not to be underestimated. It may affect the whole body's immunity and may lead to premature senility.

Work, entertainment, shopping, travel, socializing and learning (such as you who are reading this tweet), mobile phones play an important role in all aspects of our lives. You may not know that mobile phones may be affecting your health in an imperceptible way, and may even affect your lifespan.

Have you ever seen slogans such as "really protect your eyes against Blu-ray" on shopping websites when you buy a mobile phone patch? In fact, mobile phone Blu-ray does not damage eyesight, but it does affect health. We can see with the naked eye that the light emitted by mobile phones is obviously colorful, why do people often talk about only blue light?

The blue light in electronic products is first of all because there is a high proportion of blue light in the light emitted by electronic screens. The so-called blue light refers to light with a wavelength range of 450-495nm. The sun and incandescent lamps mix white light at various wavelengths, while modern electronic devices provide white backlight, whose screens rely on LED, an element that can only emit monochromatic light, which can only convert blue or ultraviolet light emitted by LED into white light, or mixed with other colors into white light. Therefore, although the backlight of these electronic screens looks white, they are actually mixed with a lot of blue light.

The second of the three ways to generate LED white light (image source: U.S. Department of Energy) is that blue light is relatively powerful. Photons of different wavelengths have different energy. the shorter the wavelength is, the higher the energy is. Blue light belongs to the stronger energy category in the wavelength range (360nm-830nm) perceived by human eyes. Some results based on cell and animal experiments have shown that high levels of exposure to blue light can induce retinal cell damage. Therefore, with the popularity of electronic products, more and more people are worried that blue light will damage their eyesight.

However, the intensity of blue light in electronic products is far from the level that can damage eyesight. Compared with the guidelines issued by the International Commission on non-Ionizing radiation Protection (ICNIRP), the blue light emission levels of these electronic devices are about 100 times lower than the harmful levels specified in the guidelines. As a result, even if you watch electronic devices for a long time, blue light does little damage to the retina. Of course, high-power LED lighting devices such as military flashlights are another matter.

However, the fact that the intensity of blue light is not strong enough to damage eyesight does not mean it will not affect the body. Because the effect of light on the human body is not limited to the formation of vision, there are non-visual effects.

The non-visual effect of light, the so-called "non-visual effect of light", refers to the long-term and acute effects of light on human physiological state (such as circadian rhythm, endocrine, etc.), behavior, emotion and other aspects that are not directly related to vision. At present, the non-visual effects of light have been used to treat related diseases, such as using specific wavelengths of light to treat circadian sleep disorders, seasonal affective disorders and dementia with specific duration and patterns. and somnolence associated with phase imbalance of circadian rhythm.

The non-visual effect of light (picture from the paper) the non-visual effect of light depends on the photosensitive substances in retinal cells. The formation of vision depends on the opsin in the cones of the retina and rhodopsin in the rod cells, which can also play a role in the non-visual effects of light. However, there is also a class of photosensitive substances-black visual proteins only play an important role in the non-visual effects of light and are most sensitive to blue light.

In 1923, researchers found that mice lacking rods and cones still contracted their pupils when exposed to light, which led to the exploration of photoreceptors other than vision. In 2002, David Berson, a neuroscientist at Brown University in the United States, discovered the third kind of photosensitive cells-light-sensitive retinal ganglion cells (ipRGC). Since then, it has opened the door for research on the non-visual effects of light.

Professor Burson found that it is this cell's perception of light that allows light to affect the circadian rhythm of mammals and synchronize them with the environment. During the day, when a specific frequency of light enters the eye, the melanin produced by ipRGC is activated to produce corresponding neuroelectrical signals, which are transmitted to the center of the hypothalamus responsible for the regulation of circadian rhythm, which in turn inhibits the synthesis and secretion of melatonin in the pineal gland, and the body enters a diurnal state.

Therefore, under normal circumstances, melatonin is mainly secreted at night, and melatonin-related physiological activities are also mainly carried out at night, which ensures that the body cycle is synchronized with the external solar cycle. Because of this, blind people with cone and rod defects can also have normal circadian rhythms and neuroendocrine.

For normal people, our electronic screens such as mobile phones emit a lot of blue light, so using mobile phones at night, even such low-intensity blue light can interfere with the body's normal circadian rhythm and reduce the quality of sleep. Circadian rhythm affects cognitive functions, including attention, execution and memory, especially blue light. Whether at night or during the day, light within 30 minutes can excite the brain. Studies have also shown that blue light suppresses melatonin production more effectively than long-wavelength light, and this nocturnal brain excitement is naturally accompanied by a decline in sleep quality. Accordingly, reducing the level of light at night and not using a cell phone before going to bed can improve sleep quality and reduce drowsiness and fatigue in the morning.

The effects of disrupting circadian rhythms changes in circadian rhythms also have a negative impact on the immune system. Under normal circumstances, the number of circulating white blood cells, the production of cytokines and the response to immunogen all have a certain circadian rhythm. Melatonin, a key regulator of circadian rhythm, can also regulate the activity of the immune system. Enhanced environmental lighting will up-regulate the expression of immune-related genes, on the contrary, prolonging the time in the dark can inhibit this immune response.

Therefore, the disruption or disturbance of circadian rhythm will induce the activation of the immune system and the production of inflammation-related cytokines, and increase the basic level of inflammation, while the chronic activation of the immune system is closely related to aging. Animal experiments have shown that interfering with genes related to intraocular circadian rhythm does shorten the lifespan of fruit flies.

In addition, animal experiments have also confirmed that prolonging the amount of light every day shortens the lifespan of fruit flies. Fruit flies exposed to continuous darkness lived 43.2% longer than those exposed to light intensity of 2000 lux, while fruit flies exposed to 12 hours of moderate blue light a day not only significantly shortened their lifespan, but also severely impaired their climbing ability. The average area of brain vacuolization (neurodegeneration) of aging fruit flies increased significantly as a result of blue light exposure.

Blue light exposure can lead to neurodegeneration in the aging Drosophila brain, with persistent darkness on the left and 12 hours of blue light exposure per day (pictured in the paper). There may be a variety of reasons for the shortened lifespan of Drosophila melanogaster. On the one hand, the prolongation of sunshine time changes the circadian rhythm of fruit flies, so that the activity of fruit flies increases, the metabolic level increases, and more free radicals are formed in the body. On the other hand, studies have shown that blue light itself causes more free radicals to be produced in the retina and even skin cells of fruit flies. These free radicals destroy mitochondrial and nuclear DNA, cell membrane and protein, accelerate aging and shorten life span of Drosophila melanogaster. Of course, more experiments are needed to confirm whether these results can be extrapolated from fruit flies to mammals, including humans.

In addition to the fact that light notes mainly affect circadian rhythm, other factors can also shorten or prolong life by affecting the mechanism of circadian rhythm, such as temperature, diet and so on. A study published in June this year shows that dietary restrictions can enhance the homeostasis of circadian rhythms in the eye, delay the aging of the visual system, reduce the systemic immune response caused by the degradation of photoreceptors in the eyes of fruit flies, and prolong the lifespan of fruit flies.

Professor Pankaj Kapahi of the Barker Aging Institute (Buck Institute for Research on Aging), one of the authors of the study, said: "staring at computer and mobile phone screens from morning till night and sustained exposure to light pollution can have a big impact on the biological clock. It not only affects eyesight, but also harms the brain and other parts of the body."

With the emergence of artificial lighting system and the rapid development of urbanization, more and more people will be affected by light pollution. It is estimated that 62% of the world's people live in a night environment that is more than 10% brighter than the natural sky, and the area and intensity of artificially illuminated outdoor areas are growing at a rate of 2.2% a year.

At the same time, more than 80% of the world's population owns smartphones, and the widespread use of these electronic screens also brings a large proportion of Blu-ray. Therefore, in such an era of light everywhere, if we want to live healthily and maintain the normal circadian rhythm of the body, we also need to take the initiative to control the light and play less with mobile phones.

Reference link:

Https://www.health.harvard.edu/blog/will-blue-light-from-electronic-devices-increase-my-risk-of-macular-degeneration-and-blindness-2019040816365

Https://medicalxpress.com/news/2022-06-uncover-intriguing-diet-eye-health.html

Reference paper:

Https://www.hindawi.com/journals/omcl/2022/8482149/

Https://pubmed.ncbi.nlm.nih.gov/24909301/

Https://pubmed.ncbi.nlm.nih.gov/35606999/

Https://pubmed.ncbi.nlm.nih.gov/30789642/https://www.sciencedirect.com/science/article/pii/S1364661309001685

Https://pubmed.ncbi.nlm.nih.gov/20463367/

Https://pubmed.ncbi.nlm.nih.gov/34731290/

Https://www.nature.com/articles/s41467-022-30975-4

Https://www.nature.com/articles/s41514-019-0038-6

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by Huang Yujia, revision: 27, clefable

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