The article describes the results of the study of the circadian rhythm of human cortisol in forced occupational sleep deprivation. The synthesis of cortisol has a clear circadian rhythm. The maximum level of production (acrophase) is observed in the first 3-4 hours after waking up. Further, a gradual decline in the concentration of the hormone occurs in the body. The minimum amount (bathyphase) is fixed in the evening and night. Changes in the synthesis of cortisol are detected in conditions of sleep deprivation in the human body. This serves as a marker for numerous and diverse functional abnormalities. The survey involved 235 male rescue firefighters aged 25 to 45 years with a service record of 1 to 22 years of the Federal Firefighting Service of the Ministry of Emergencies in the Tver Region. The subjects were divided into three groups. In the first group there were persons with an experience of 1 to 6 years (the stage of professional adaptation and), in the second with an experience of 7-15 years (the level of professionalism formed) and in the third with an experience of 16-22 years (a period of possible professional “burnout and destruction "). Seven times every four hours, saliva collected from firefighters-rescuers. Then the level of free salivary cortisol was measured using enzyme-linked immunosorbent assay. The first and last saliva collection was at 8 a.m. at the beginning and end of the daily work shift. The study showed that in a situation of daily hard work and forced sleep deprivation, group chronograms corresponded to the normal circadian rhythm of cortisol with a morning rise in its synthesis. For rescue firefighters with 7-15 years of service, the average group acrophase amplitude of the daily curve was significantly lower compared to other respondents (5.132±0.098; 2.002±0.085; 9.322±0.199 ng/ml in the first, second and third groups; normal values: 2.80 – 7.70 ng / ml). Stable low values of cortisol levels were found in 90 % of firefighter-rescuers with 7–15 years of service in the morning at the beginning of the shift and at the end of the shift. This probably means saving reserves by lowering the tone of the hypothalamus, pituitary and adrenal glands. Less homogeneous and stable indicators were found in the examined individuals with 1-6 years of service and 17-22 years of service. A high level of the hormone was detected in almost 30 % of firefighter-rescuers with 1-6-year service experience at the beginning of the working day. It was a marker of chronic stress. The work shows that signs of desynchronosis were found in a number of individuals according to the architectonics of the daily curve of cortisol. The phenomena of abnormal circadian production of glucocorticoid gradually increased with an increase in experience. This was noted in persons with an experience of 17-22 years in almost half the cases (7, 10 and 46 % of persons in the first, second, third groups). This was probably due to the cumulative effect of negative phenomena, including forced sleep deprivation, which reduces the chronobiological resistance of the body.

Vlasenko Natalya Yurievna, Candidate of Sciences (Biology), Associate Professor, Tver State Technical University, 22, Afanasiy Nikitin emb., Tver, 170026, Russian Federation, e-mail: natalya_vlasenko@mail.ru 

Vlasenko Mariya Aleksandrovna, Student, N. I. Pirogov Russian National Research Medical University, 1, Ostrovityanov st., Moscow, 117997, Russian Federation, e-mail: mar_vlasenko@mail.ru

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