Introduction. Living in the northern territories is associated with chronic stress.The stressors are the natural climatic factors of the north: a long period of low temperatures, strong winds, pronounced dynamics of atmospheric pressure, altered photoperiod. In the development of a stress response, stress-realizing and stress-limiting systems are distinguished. Their dynamics make it possible to assess when the body is most vulnerable to the adverse effects of extreme environmental factors to take preventive measures in a timely manner.

Materials and methods.The components of stress-realizing and stress-limiting systems were studied in students of a northern university under conditions of short (December) and long (May) daylight hours. The secretion of melatonin was assessed using the enzyme immunoassay method based on the concentration of 6-sulfatoxymelatonin in urine, the autonomic regulation of heart rhythm was studied using indicators of heart rate variability, and anxiety was studied using the Spielberger’s scale for assessing the level of state (reactive) and trait anxiety (adapted by Yu.L. Khanin).

Results. There was revealed the trend in the concentration of 6-sulfatoxymelatonin in urine: in the male and female groups the indicator decreases from December to May. In conditions of long daylight hours, state (reactive) and trait anxiety among female students decreased, while the level of anxiety among male students remained more stable. In Spring the young women’s parasympathetic influences was found to weaken, while sympathetic activity remained. In the male group, the length of daylight didn’t affect the spectral characteristics.

Limitations. Male and female higher education students in the northern region.

Conclusion. Intersexual features of the implementation of mechanisms of stress-realizing and stress-limiting systems were discovered during a critical violation of the parity of light and dark time of day. The photoperiod of the north must be considered from a hygienic aspect, to prevent deterioration in public health due to a decrease in the activity of a number of stress-limiting mechanisms. The risk of disruption of the functions chronostructure elevates with increasing predominance of daylight hours over darkness; the probability of the formation of exogenous desynchronosis increases in late Spring – early Summer. It is necessary to increase public awareness regarding the role of melatonin in the functioning of the body and hygienic ways to correct its level in the conditions of the asymmetric photoperiod of the north.

Compliance with ethical standards. The study was conducted in accordance with the ethical and legal standards set out in the World Medical Association Declaration of Helsinki.Respondents gave informed, voluntary written consent to participate in the study and publish personal information in anonymized form.The study was approved by the local ethics committee of the Nizhnevartovsk State University (Protocol No. 1 dated September 12, 2022).

Contribution: Ragozin O.N. – research concept, editing; Shalamova E.Yu., Pogonysheva I.A. – research design, collection of primary materials, text writing, editing; Kudyasheva V.P., Pogonyshev A.D. – preparation of primary data for statistical processing, statistical processing and analysis of results. All co-authors – approval of the final version of the article, responsibility for the integrity of all parts of the article.

Conflict of interest. The authors declare no conflict of interest.

Acknowledgment. The study was carried out at the expense of the grant of the Russian Science Foundation and the Government of Khanty-Mansi Autonomous Okrug – Yugra No. 22-15-20023.

Received: May 2, 2024 / Revised: May 27, 2024 / Accepted: October 2, 2024 / Published: March 7, 2025