The discrepancy between biological and social rhythms known as social jetlag (SJL) is common in modern society and has a range of negative consequences for cognitive functioning, well-being and health. Social jetlag is typical for people with late chronotypes. As shown earlier, the prevalence of individuals with a late chronotype is higher among the residents of high latitudes. Therefore, a higher rate of detection of people with SJL should be expected in the North. In this study we assessed the detection rate of SJL among 62 young inhabitants of the European North of Russia (the Komi Republic), and the relationship between SJL, the circadian rhythm of the wrist temperature, and the cortisol awakening response (CAR). The detection rate of SJL was 65% among the people examined. A significant decrease in the amplitude (A) of circadian rhythm of wrist temperature: (β = −0.34 (CI 95%: −0.66 to −0.33); F_1,60 = 10.4; p < 0.0001; η² = 0.31), an increased incidence of depression: No-SJL = 4.5%; SJL = 17.5% (H = 4.84; p < 0.05), and a tendency for an increase in CAR was also observed in the SJL group. There were sex differences in sensitivity to SJL. Females with SJL but not males had higher global seasonality scores (β = 0.51 (CI 95%: 0.21 to 0.81); F_1,33 = 10.9; p < 0.002; η² =0.24), shorter sleep duration (β = −0.52 (CI 95%: −0.82 to −0.22); F_1,33 = 12.9; p < 0.001; η² = 0.28), worse sleep quality (β = 0.39 (CI 95%: 0.07 to 0.72); F_1,33 = 6.31; p < 0.017; η² = 0.16) and lower A of circadian rhythm of wrist temperature (β = −0.18 (CI 95%: −0.55 to 0.18); F_1,33 = 4.48; p < 0.043; η² = 0.13) compared with females without SJL. Thus, our data indicate that 40 of 62 participants of investigation had social jetlag. A decrease of the amplitude of the circadian rhythm of the wrist temperature appears to be an objective marker of SJL. Social jetlag had a strong negative impact on females but not on males.

The study examined eating timing, diet, and the ratio of sleep phases in people with social jetlag (SJL). The study involved 83 participants who filled out a questionnaire, and 21 of them took part in the study of sleep phases by electroencephalography during the week. SJL was associated with a higher incidence rate of eating jetlag, eating phase delays, an increase in calorie intake after 9 p.m., a decrease in dietary fiber intake for breakfast, and melatonin-containing product consumption for dinner. Young people with SJL had a reduction in total sleep and light sleep phase duration by 60 and 36 min on work/school days and an increase in total sleep and REM sleep phase duration by 66 and 60 min on weekends, respectively. Young people consuming foods with more than 4234.5 ng of melatonin for dinner, compared with their peers consuming less than 313.2 ng of melatonin, showed a decrease in SJL and sleep debt by 54 and 90 min and an increase in the total sleep and the deep sleep phase duration by 66 and 30 min, respectively. Thus, the consumption of melatonin-containing foods for dinner is associated with a decrease in circadian misalignment and a sleep quality improvement.