Life before and after COVID-19: The ‘New Normal’ Benefits the Regularity of Daily Sleep and Eating Routines among College Students

After the COVID-19 lockdown, a ‘new normal’ was established, involving a hybrid lifestyle that combined face-to-face with virtual activity. We investigated, in a case-control study, the impact of the ‘new normal’ on daily sleep and eating routines, compared with pre-pandemic conditions. To do this, we propose using social and eating jet lag as markers of the regularity in daily routines. Additionally, we studied whether the ‘new normal’ had an impact on the body mass index (BMI), diet quality, and other health-related variables. This study included 71 subjects in the pre-pandemic group, and 68 in the ‘new normal’ group (20–30 years). For all participants, we evaluated social and eating jet lag, BMI, diet and sleep quality, eating behaviors, physical activity, and well-being. General linear models were used to compare outcome variables between pre-pandemic and ‘new normal’ groups. The results revealed that the ‘new normal’ was associated with greater regularity in daily sleep and eating routines (−0.7 h of social jet lag (95% CI: −1.0, −0.4), and −0.3 h of eating jet lag (95% CI: −0.5, −0.1)), longer sleep duration on weekdays (1.8 h (95% CI: 1.5, 2.2)), and lower sleep debt (−1.3 h (95% CI: −1.7, −0.9)). Regarding BMI and other health-related variables, we observed that these variables were similar between ‘new normal’ and pre-pandemic groups. These findings indicate that the ‘new normal’ had a positive impact on daily sleep and eating routines. Additionally, our results indicated that the ‘new normal’ offered college students a more sustainable lifestyle, which was associated with more hours of sleep during the week and lower sleep debt. This, in the long run, could have a positive impact on BMI and overall health.

Evaluation of sleep characteristics of children and adolescents with type 1 diabetes mellitus

ABSTRACT Objective: To evaluate sleep characteristics of children and adolescents with type 1 diabetes mellitus (T1DM) and their relationship with glycemic control. Methods: A cross-sectional study was conducted at a public hospital in São Paulo, Brazil. It included 86 patients with T1DM, aged between 10 and 18 years old, who were on insulin therapy, had performed at least three measurements of capillary blood glucose throughout the day, and had normal thyroid function. The clinical, anthropometric, and laboratory data of each patient were evaluated. The Pediatric Daytime Sleepiness Scale (PDSS) and the Munich Chronotype Questionnaire (MCTQ) were used to assess the sleep characteristics. Results: The mean level of glycated hemoglobin (HbA1c) was 9.2±2.1%, and it was higher in adolescents than in children. The mean score of PDSS was 13.9±4.7. Patients with HbA1c<7.5% had lower PDSS scores and longer sleep duration on weekdays than patients with HbA1c≥7.5%. HbA1c levels were negatively correlated with chronotype values and sleep duration on weekdays and positively correlated with social jet lag. Patients who had had T1DM for less than three years had a higher prevalence of daytime sleepiness. The regression analysis showed that higher HbA1c (≥7.5%) and shorter time since the diagnosis of T1DM increased the chance of daytime sleepiness, regardless of age and sex. Conclusions: Patients with higher HbA1c had more daytime sleepiness, a morning chronotype, shorter sleep duration on weekdays and a more significant social jet lag. The shorter diagnosis time for T1DM and greater levels of HbA1c increased the chance of daytime sleepiness.

A Mathematical Model to Characterize the Role of Light Adaptation in Mammalian Circadian Clock

In response to a light stimulus, the mammalian circadian clock first dramatically increases the expression of Per1 mRNA, and then drops to a baseline even when light persists. This phenomenon is known as light adaptation, which has been experimentally proven to be related to the CRTC1-SIK1 pathway in suprachiasmatic nucleus (SCN). However, the role of this light adaptation in the circadian rhythm remains to be elucidated. To reveal the in-depth function of light adaptation and the underlying dynamics, we proposed a mathematical model for the CRTC1-SIK1 network and coupled it to a mammalian circadian model. The simulation result proved that the light adaptation is achieved by the self-inhibition of the CRTC1/CREB complex. Also, consistently with experimental observations, this adaptation mechanism can limit the phase response to short-term light stimulus, and it also restricts the rate of the phase shift in a jet lag protocol to avoid overly rapid re-entrainment. More importantly, this light adaptation is predicted to prevent the singularity behavior in the cell population, which represents the abolishment of circadian rhythmicity due to desynchronization of oscillating cells. Furthermore, it has been shown to provide refractoriness to successive stimuli with short gap. Therefore, we concluded that the light adaptation generated by the CRTC1-SIK1 pathway in the SCN provides a robust mechanism, allowing the circadian system to maintain homeostasis in the presence of light perturbations. These results not only give new insights into the dynamics of light adaptation from a computational perspective but also lead us to formulate hypotheses about the related physiological significance.

Light intensity alters the effects of light-induced circadian disruption on glucose and lipid metabolism in mice

Circadian disruption induced by rotating light cycles has been linked to metabolic disorders. However, how the interaction of light intensity and light cycle affects metabolism under different diets remains to be explored. Eighty mice were first randomly stratified into the low- (LFD, n = 40) or high-fat diet (HFD, n = 40) groups. Each group was further randomly subdivided into four groups (n = 8-12 per group) in terms of different light intensities (lower [LI, 78 lx] or higher intensity [HI, 169 lx]) and light cycles (12 h light:12 h dark cycle or circadian-disrupting [CD] light cycle consisting of repeated 6-h light phase advancement). Body weight was measured weekly. At the end of the 16-week experiment, mice were sacrificed for serum and pathological analysis. Glucose and insulin tolerance tests were performed during the last 2 weeks. The CD cycle increased body weight gain, adipocyte area, glucose intolerance, and insulin resistance of LFD as well as HFD mice under HI but not LI condition. Moreover, the serum and hepatic triglyceride levels increased with LFD-HI treatment, regardless of light cycle. In addition, the CD cycle improved lipid and glucose metabolism under HFD-LI condition. In summary, the detrimental effects of the CD cycle on metabolism were alleviated under LI condition, especially in HFD mice. These results indicate that modulating light intensity is a potential strategy to prevent the negative metabolic consequences associated with jet lag or shift work.

Alterações do Ritmo Circadiano no Atleta

Sleep is very important for the proper functioning of the human body and consists of several stages. This text will address the concepts of biological rhythms, the circadian rhythm and body temperature, which is considered the main biological marker of the circadian rhythm. Their disorders have an influence on the athlete’s performance, with jet lag being approached. The diagnosis of these disorders can be made through various subjective and objective methods. Finally, adaptation strategies will be mentioned, addressing physical exercise, diet, and medication, among others.

Implementing a Circadian Adaptation Schedule after Eastward Flight in Young Male Athletes

This study examined the effectiveness of a circadian adaptation schedule in male cricketers after an 8.5 h eastward time zone change. Ten participants (aged 18.7 ± 0.9 y) were randomly assigned to a control group or an intervention group. Participants in the intervention group followed a light exposure schedule in which they were instructed to seek light in the three hours preceding, and avoid light in the three hours following their estimated core body temperature minimum. The rate of adaptation was assessed using the nightly excretion rate of urinary 6-sulphatoxymelatonin (aMT6s). General linear mixed models were conducted to assess the effect of condition (i.e., control and light intervention) on nocturnal secretion of aMT6s. Significant main effects of day (F(7, 35) = 10.4, p < 0.001) were reflected by an increase in nocturnal melatonin excretion (i.e., all participants gradually adapted to the destination time zone). Subjective jet lag decreased by day (F(7, 54) = 22.9, p < 0.001), bedtime was delayed by day (F(7, 54) = 3.1, p = 0.007) and get up time was earlier by day (F(7, 35) = 5.4, p < 0.001). On average, it took 7 days for all participants to return to baseline levels following transmeridian travel. Similarly, it took 7 days for subjective jet lag to alleviate. In the initial 4 days of the protocol, the intervention group registered higher levels of nocturnal urinary melatonin, however, there was no significant differences in the rate of adaptation between the groups. It is possible that participants did not adhere to the intervention or that they followed the intervention but it was ineffective.

Beyond the limits of circadian entrainment: Non-24-hour sleep-wake disorder, shift work, and social jet lag

While the vast majority of humans are able to entrain their circadian rhythm to the 24-hour light-dark cycle, there are numerous individuals who are not able to do so due to disease or societal reasons. We use computational and mathematical methods to analyze a well-established model of human circadian rhythms to address cases where individuals do not entrain to the 24-hour light-dark cycle, leading to misalignment of their circadian phase. For each case, we provide a mathematically justified strategy for how to minimize circadian misalignment. In the case of non-24-hour sleep-wake disorder, we show why appropriately timed bright light therapy induces entrainment. With regard to shift work, we explain why reentrainment times following transitions between day and night shifts are asymmetric, and how higher light intensity enables unusually rapid reentrainment after certain transitions. Finally, with regard to teenagers who engage in compensatory catch-up sleep on weekends, we propose a rule of thumb for sleep and wake onset times that minimizes circadian misalignment due to this type of social jet lag. In all cases, the primary mathematical approach involves understanding the dynamics of entrainment maps that measure the phase of the entrained rhythm with respect to the daily onset of lights.

Jet-Lag Countermeasures Used by International Business Travelers

INTRODUCTION: Research has highlighted the significant impact that jet lag can have upon performance, health, and safety. International business travelers have an important role in economic growth; however, there is a lack of research investigating jet lag and jet-lag management in international business travelers. This study aimed to investigate international business travelers use of jet-lag countermeasures. METHODS: International business travelers from Australia (N = 107) participated in a survey examining use of jet-lag countermeasures (pharmacological and nonpharmacological). Chi-squared tests were conducted examining the association between duration of stay and traveling experience on jet-lag countermeasure use. RESULTS: Most subjects had traveled for business for less than 15 yr and 57% reported taking between 14 trips annually. Durations of stay averaged 10 d (SD 13 d). Nonpharmacological countermeasure use was high. Pharmacological countermeasure use was less common. There were no significant associations between duration of stay and countermeasure implementation. Travel experience was only associated with nonpharmacological countermeasures after arrival home. CONCLUSION: Education programs delivered through businesses would be beneficial for providing information on jet lag, its implications, and recommended countermeasures to travelers. Rigney G, Walters A, Bin YS, Crome E, Vincent GE. Jet-lag countermeasures used by international business travelers. Aerosp Med Hum Perform. 2021; 92(10):825830.