Later school start time is associated with better academic performance, sleep-wake rhythm characteristics, and eating behavior.

There are numerous studies which show that an early school start time has a negative impact on the sleep, well-being, and academic performance of students. There is not enough information on the association between school start time and eating disorders, however: the disruption of the circadian rhythm is known to be a risk factor for eating disorders. The aim of this study is to analyze the relationship between school start time (SST) and the sleep, well-being, academic performance, and eating behavior of children and adolescents. The study was conducted in April and May 2021 in two regions of Russia: the Komi Republic and Yekaterinburg. The online study involved the anonymous and voluntary participation of 6571 students in grades 6-11 (mean age: 14.5 ± 1.6 years, 60.1% female), who have morning classes. All participants were divided into three groups according to SST: 08:00 (n = 3661), 08:30 (n = 2020), and 09:00 (n = 890). Each participant of the study indicated their place of residence, SST, age, sex, height, weight, academic performance, and filled out the Munich Chronotype Questionnaire, the Zung Self-Rating Depression Scale, and the Yale Food Addiction Scale for Children. As a result of multiple regression analysis, it was shown that schoolchildren with SST of 09:00 wake up at a later time on school days (B = 0.432; ΔR2 = 0.039), sleep more (B = 0.293; ΔR2 = 0.004), have less pronounced social jetlag (B = -0.223; ΔR2 = 0.005) and sleep loss (B = -0.292; ΔR2 = 0.005), and higher academic performance (B = 0.113; ΔR2 = 0.003) than schoolchildren with SST of 08:00. As a result of logistic regression analysis, it was found that the frequency of the detection of food addiction is ~30% lower in schoolchildren with SST of 09:00 (OR = 0.690; 95% CI = 0.485-0.981) than in their peers with SST of 08:00. Thus, an overly early SST in Russia has a negative impact on the sleep function, academic performance, and eating behavior of children and adolescents.

Chronotype, social jetlag, and time perspective.

The phase of entrainment (chronotype) is known to be associated with time perspective (TP), suggesting that the state of circadian system is involved in the long-term planning of human life. However, little is known regarding the influence of circadian misalignment on long-term planning ability. The aim of this study was to investigate the association between social jetlag (SJL) and TP. A total of 1064 schoolchildren and university students (mean age ± standard deviation, 19.2 ± 2.9 years; range, 15-25 years; females, 71.7%) from four cities in the Russian Federation located between 56.9 and 61.7 degrees North completed the Munich ChronoType Questionnaire, the Pittsburgh Sleep Quality Index, the Seasonal Pattern Assessment Questionnaire, and Zimbardo Time Perspective Inventory. Study participants also indicated personal data (age, sex, height weight, place of residence, and achievements). A multiple regression analysis with stepwise inclusion of predictors in the model was performed to evaluate associations between time perspective characteristics (dependent variables) and predictor variables. The change in R2 was used as the measure of effect size. Chronotype was found to be a moderate predictor of future TP (B = 0.034; ΔR2 = 0.037). In addition, sleep quality was found to be a moderate predictor of past negative (B = 0.043; ΔR2 = 0.074), present fatalistic (B = 0.021; ΔR2 = 0.035), and deviation from balanced TP (B = 0.034; ΔR2 = 0.066). Mood seasonality was a moderate predictor of present hedonistic TP (B = 0.016; ΔR2 = 0.038), and social jetlag was a weak predictor of present fatalistic (B = 0.052; ΔR2 = 0.019), future (B = -0.033; ΔR2 = 0.004), and deviation from balanced TP (B = 0.047; ΔR2 = 0.012). In conclusion, this study found a weak but significant association between social jetlag and TP in adolescents and young adults.