RUDN doctors have discovered that LED light and device screens changes circadian rhythms and the functioning of the cardiovascular system. In an experiment with laboratory rats, doctors found that blue light affects blood pressure, pulse and hormone production. This is especially noticeable with concomitant hypertension. The results are published in Pathophysiology .

All biological processes in the body are subject to cyclic changes that are associated with the change of day and night. One of the key regulatory mechanisms of these processes is the hormone melatonin. The more light, the less melatonin the body produces. Moreover, not only the intensity of light itself is important, but also its spectrum. Under natural conditions, light “turns red” in the evening: the blue part of the spectrum disappears from it, which corresponds to waves with a shorter wavelength. However, modern LED lamps and device screens have a blue light. RUDN University doctors studied how “they affect the vital activity of animals, especially if they already have primary signs of high blood pressure — hypertension.

“Under natural conditions, short waves gradually disappear towards evening. However, in the modern world, the blue part of the spectrum lasts much longer, mainly due to artificial light and electronic LED devices. Currently, there is no clear understanding of how too long exposure to light with a predominance of short waves affects the chronostructure of the cardiovascular and excretory systems in primary hypertension,” Mikhail Blagonravov, MD, Head of the Department of General Pathology and Pathological Physiology at RUDN University said. 

For the experiment, the physicians used 20 rats, ten of which had hypertension. All animals lived in single cages with alternating periods of "day" and "night" lasting 12 hours. The experiment was carried out twice, first with normal daylight and then with blue light. For seven days, the rats were measured for blood pressure and electrolyte levels in the urine, an electrocardiogram was taken, and other tests were performed.

In healthy rats, under the influence of blue light, the average daily and nighttime blood pressure decreased. The most noticeable change was in the heart rate - the pulse in animals with hypertension decreased by 10-20%. For all rats, melatonin levels also changed significantly. In healthy individuals, melatonin levels were reduced by exposure to blue light, while in hypertensive rats, it increased during the day and decreased at night.

“Changes in the dark-light cycle cause both acute and chronic changes in the melatonin rhythm. Light with certain characteristics can both delay and speed up the circadian system. Our experiment showed that long-term exposure to blue light during the day affects not only the circadian rhythms of the cardiovascular system, but also the rhythm of electrolyte release and melatonin production, both in normal and elevated blood pressure. We also found that blood pressure and pulse are less dependent on monochromatic light in animals with primary hypertension,” Anna Bryk, PhD, Assistant Professor, Department of General Pathology and Pathological Physiology at RUDN University said.

Journal Link: Pathophysiology 2022, 29(1), 118-133