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Bright screens of computer devices emit short wave blue light that affects sleep via disrupting melatonin secretion. Changes of lifestyle could help to avoid this negative effect.

Many people find their sleep patterns disturbed these days. Getting to bed very late at night, waking up often during the sleep or simply being unable to fall asleep for very long time seem to be typical problems of many office workers. Recent research suggests that this can directly correlate with the use of bright computer screens late in the evening.

Findings published by researchers from the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, NY, demonstrate that working with light-emitting devices such as tablets, laptops and desktop computer screens in the evening affects normal production of melatonin, the hormone involved in the regulation of sleep cycle.

Just two hours of working with iPad at maximum brightness significantly disrupts melatonin secretion.

What is melatonin? Where it is produced in the brain? How it works?

Melatonin is a simple organic compound which plays an important role in the body. It is produced by pineal gland located in the center of the brain. Melatonin production is inhibited by light and stimulated by darkness. Due to this correlation, melatonin is called sometimes the “darkness hormone”. Obviously, due to the location of gland in the center of brain, light cannot reach there.

Photosensitive cells of the eye retina send the signals regarding the level of light to pineal gland via several neuronal connections in central nervous system and spinal cord. One of the important connecting points is suprachiasmatic nuclei (SCN), the "master clock" of circadian rhythm. Circadian rhythm is the body’s sleep and wake cycle. SCN sets the body clock, and melatonin plays a role of adjusting mechanism. Melatonin helps to “reset” the clock, for example when we cross several time zones during traveling. Jet lag experienced by travelers is directly connected to the readjustment of circadian clocks with the help of melatonin. Melatonin synchronizes circadian cycle with the real cycle of day and night experienced by the body.

Circadian cycle can be “fooled”

Due to the connection between melatonin production and light exposure, circadian cycle can be “fooled” by excessive exposure to artificial light. This is exactly what happens if we use light emitting devices like laptop computers and tablets in the evening. Exposure to light at this time of the day leads to the decrease in melatonin level, sending a wake-up signal to SCN.

Why computer screens have such a significant effect on the level of melatonin? After all, evening exposure to other light sources does not affect our sleep too much. It seems that the answer to this question lies not just in the intensity of light, but also in its wavelength.

Other scientific research has shown that production of melatonin is affected not simply by light in general but by the short wave blue light (with wavelength at approximately 470 nm). This is the bluish-white type of light generated by the screens of many of our computer devices.

Continue reading after recommendations

  • Arendt J. (2006) Melatonin and human rhythms. Chronobiol Int. 23(1-2): 21-37
  • 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
  • Glickman G, Levin R, Brainard GC. (2002) Ocular input for human melatonin regulation: relevance to breast cancer. Neuro Endocrinol Lett. 23 (Suppl 2): 17-22
  • Skene DJ, Arendt J. (2006) Human circadian rhythms: physiological and therapeutic relevance of light and melatonin. Ann Clin Biochem. 43(Pt 5): 344-53
  • 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
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