PETROZAVODSK, September 22. /TASS/. Excessive artificial or natural blue light affects Arctic residents in winter. The effect increases in the evening and leads to an increase in bad cholesterol and to other changes, senior researcher at the Laboratory of Genetics, the Institute of Biology (the Russian Academy of Sciences' Karelian Scientific Center), Sergey Kolomeychuk told TASS.

Blue light gives signals the body about the coming period of activity. The light may come from both natural and artificial sources, such as gadgets. At late hours, it activates the receptor, disrupts the biological rhythm and affects human health. This problem is especially relevant in the extreme light conditions of the Arctic, with its white and polar nights, scientists say.

"In the northern regions, in addition to artificial light pollution, there is natural light pollution. We receive excessive blue spectrum light, which, so to speak, is a harmful and unfavorable factor affecting health. The most dangerous for humans is time from 21:30 to 01:00 in winter," the scientist noted.

The researchers used actigraphs - wristwatch-like devices to record rest/activity cycles, light exposure, body temperature, and movement. Reference rates were weekly and daily data during the spring and autumn equinoxes, as well as the winter and summer solstices. This way, the researchers analyzed maximum and minimum periods of solar activity. Obtained results allowed scientists to identify seasonal changes.

In the evening in winter, people had excess glucose, and higher levels of bad cholesterol and triglycerides, as well as high stress hormone - cortisol. However, in the morning during the summer solstice, the situation was opposite. At that time, scientists recorded a glucose deficiency.