Impact on health outcomes associated with changing the clock 1 hour during fall and spring transitions in the Southern Hemisphere.

STUDY OBJECTIVES: Changing the clocks seasonally is potentially harmful because it interferes with normal daytime activities. Studies aimed at quantifying this association are scant. The objective of this study was to determine the effects of 1 year's worth of changing the clocks (fall and spring transitions) on healthy young men located in the Southern Hemisphere in South America. METHODS: We performed an observational prospective study. Thirty healthy male university students were evaluated from 2 weeks before to 2 weeks after both the fall and spring transitions. We administered an overall sleep questionnaire, assessed quality of life, recorded 7-day wrist actigraphy, and had participants perform a psychomotor vigilance task. We defined the 1-hour clock change as the primary exposure and the change in psychomotor vigilance task lapses of 500 milliseconds or more in response time as our primary outcome. Changes were evaluated by the Wilcoxon rank test (significance: P < .05). RESULTS: After the fall transition, we found a significant worsening in psychomotor vigilance task performance (median [interquartile range], 9.9 [6.0-14.3] lapses of ≥ 500 milliseconds in response time at baseline vs 16.8 [8.2-28.0] after transition; P < .002). Additionally, we found a median loss of about 1 hour of total sleep time and time in bed after the fall transition. Furthermore, participants presented with insomnia. Performance on the psychomotor vigilance task was also affected after the spring transition (16.7 [10-23] vs 23 [12.2-32.2]; P < .001). CONCLUSIONS: A decrease in performance in neurocognitive tests was found after both time transitions. The transition led to insomnia and a significant worsening of sleep variables. CITATION: Labarca G, Henriquez-Beltrán M, Sanhueza R, et al. Impact on health outcomes associated with changing the clock 1 hour during fall and spring transitions in the Southern Hemisphere. J Clin Sleep Med. 2024;20(6):887-893.

12-week melatonin administration had no effect on diabetes risk markers and fat intake in overweight women night workers.

Introduction: Interactions between circadian clocks and key mediators of chronic low-grade inflammation associated with fat consumption may be important in maintaining metabolic homeostasis and may pose a risk for the development of obesity-associated comorbidities, especially type 2 diabetes (T2DM). Objective: The aims of the present study were to evaluate the effects of melatonin administration on diabetes risk markers according to dietary lipid profile (pro-inflammatory versus anti-inflammatory) in excessive weight night workers, and to determine the effect of administration on fat consumption profile. Methods: A randomized, controlled, double-blind, crossover clinical trial involving 27 nursing professionals working permanent night shifts under a 12×36-hour system. The melatonin group (12 weeks) used synthetic melatonin (3 mg) only on days off and between shifts, while the placebo group (12 weeks) was instructed to take a placebo, also on days off and between shifts. For inflammatory characteristics, participants were divided into pro-inflammatory (saturated fats, trans fats and cholesterol) and anti-inflammatory (monounsaturated, polyunsaturated fats and EPA + DHA) groups according to fatty acid determinations. At baseline and at the end of each phase, blood glucose, insulin, glycosylated hemoglobin plasma concentrations were collected, and HOMA-IR was calculated. Conclusion: Melatonin administration for 12 weeks had no effect on T2DM risk markers according to dietary lipid profile (pro-inflammatory or anti-inflammatory potential) in excessive weight night workers. Among the limitations of the study include the fact that the low dose may have influenced the results expected in the hypothesis, and individual adaptations to night work were not evaluated. The insights discussed are important for future research investigating the influence of melatonin and fats considered anti- or pro-inflammatory on glucose and insulin homeostasis related to night work.

Minor Changes in Daily Rhythms Induced by a Skeleton Photoperiod Are Associated with Increased Adiposity and Glucose Intolerance.

Eating during the rest phase is associated with metabolic syndrome, proposed to result from a conflict between food consumption and the energy-saving state imposed by the circadian system. However, in nocturnal rodents, eating during the rest phase (day-feeding, DF) also implies food intake during light exposure. To investigate whether light exposure contributes to DF-induced metabolic impairments, animals receive food during the subjective day without light. A skeleton photoperiod (SP) is used to entrain rats to a 12:12 cycle with two short light pulses framing the subjective day. DF-induced adiposity is prevented by SP, suggesting that the conflict between light and feeding stimulates fat accumulation. However, all animals under SP conditions develop glucose intolerance regardless of their feeding schedule. Moreover, animals under SP with ad libitum or night-feeding have increased adiposity. SP animals show a delayed onset of the daily rise in body temperature and energy expenditure and shorter duration of nighttime activity, which may contribute to the metabolic disturbances. These data emphasize that metabolic homeostasis can only be achieved when all daily cycling variables are synchronized. Even small shifts in the alignment of different metabolic rhythms, such as those induced by SP, may predispose individuals to metabolic disease.

Leptin and adiponectin regulate the activity of nuclei involved in sleep-wake cycle in male rats.

Epidemiological and experimental evidence recognize a relationship between sleep-wake cycles and adiposity levels, but the mechanisms that link both are not entirely understood. Adipose tissue secretes adiponectin and leptin hormones, mainly involved as indicators of adiposity levels and recently associated to sleep. To understand how two of the main adipose tissue hormones could influence sleep-wake regulation, we evaluated in male rats, the effect of direct administration of adiponectin or leptin in the ventrolateral preoptic nuclei (VLPO), a major area for sleep promotion. The presence of adiponectin (AdipoR1 and AdipoR2) and leptin receptors in VLPO were confirmed by immunohistochemistry. Adiponectin administration increased wakefulness during the rest phase, reduced delta power, and activated wake-promoting neurons, such as the locus coeruleus (LC), tuberomammillary nucleus (TMN) and hypocretin/orexin neurons (OX) within the lateral hypothalamus (LH) and perifornical area (PeF). Conversely, leptin promoted REM and NREM sleep, including increase of delta power during NREM sleep, and induced c-Fos expression in VLPO and melanin concentrating hormone expressing neurons (MCH). In addition, a reduction in wake-promoting neurons activity was found in the TMN, lateral hypothalamus (LH) and perifornical area (PeF), including in the OX neurons. Moreover, leptin administration reduced tyrosine hydroxylase (TH) immunoreactivity in the LC. Our data suggest that adiponectin and leptin act as hormonal mediators between the status of body energy and the regulation of the sleep-wake cycle.

Adolescent sleep timing and dietary patterns in relation to DNA methylation of core circadian genes: a pilot study of Mexican youth.

Mistimed sleep/wake and eating patterns put shift workers at increased risk for cardiometabolic disease, and epigenetic modification of circadian genes has been proposed as a mechanism. Although not as extreme as shift workers, adolescents often have delayed sleep timing and irregular eating patterns. The aim was to assess whether sleep midpoints - median of bed and wake time - and dietary patterns in adolescents were associated with DNA methylation of circadian genes. The study population included 142 Mexican youth (average age of 14.0 (SD = 2.0) years, 49% male). Average sleep midpoint over weekdays was estimated with actigraphy. Diet was assessed with a semi-quantitative food frequency questionnaire, and three dietary patterns were derived from principal component analysis, a Plant-based & lean proteins pattern, a Meat & starchy pattern, and an Eggs, milk & refined grain pattern. DNA methylation was quantified in blood leukocytes with the Infinium MethylationEPIC BeadChip, and data from 548 CpG sites within 12 circadian genes were examined. Linear regression analyses, adjusted for sex, age, and % monocytes, showed that later sleep timing was associated with higher DNA methylation of several circadian genes, notably with RORB, PER1, CRY2, and NR1D1. Each of the dietary patterns examined was also related to circadian gene DNA methylation, but the Eggs, milk & refined grain pattern ('breakfast' pattern) had the clearest evidence of relationships with circadian genes, with inverse associations (lower DNA methylation) across all 12 genes. Findings suggest that timing-related sleep and eating behaviours among adolescents could result in epigenetic modification of clock genes.

Is social jetlag similar to travel-induced jetlag? Results of a validation study.

Social jetlag (SJL) is defined as the misalignment between the biological clocks and the social clock imposed by work and social constraints. In order to accomplish the workdays duties, people tend to not respect the internally sleep-wake cycle during the week, often using alarm clock to wake-up, which would lead to a chronic form of travel-induced jetlag. This circadian misalignment has been found to be associated with increased health risk and health-impairing behaviors. In this cross-sectional study, we aimed to explore whether the SJL is a valid concept for the travel-induced jetlag symptoms, as well as what is the cutoff point with best parameters for defining the presence of SJL, in a sample of undergraduate students of a university in Southern Brazil. We assessed SJL by the Munich ChronoType Questionnaire (MCTQ) and defined the concept as the difference between the midsleep point on free days and the midsleep point on classes days. The gold standard was defined as having at least one travel-induced jetlag symptom (fatigue, sleepiness or difficulty concentrating). Relative SJL, sensitivity and specificity were calculated for different cutoff points, plotted on ROC curves. A total of 452 students with complete sleep information were included in the analysis. The relative SJL mean was 2 h 23 min (SD = 1 h 24 min; range -3 h to 7 h 58 min) and 63.7% of the students had ≥2 h of relative SJL. All the tested cutoff points of the instrument had low sensitivity and specificity values, covering a small area under the ROC curve (0.487). The best parameters were for the cutoff point ≥2 h, with 63.4% sensitivity and 35.9% specificity. SJL did not revealed to be a valid concept for the studied sample comparing it to travel-induced jetlag symptomatology. One possible explanation for the lack of validity of our results regards the fact that SJL may not have the same apparent wide-term effects as the travel-induced jetlag. Then, the symptoms of SJL do not well represent the symptoms of travel-induced jetlag.

Wearable technologies for developing sleep and circadian biomarkers: a summary of workshop discussions.

The "International Biomarkers Workshop on Wearables in Sleep and Circadian Science" was held at the 2018 SLEEP Meeting of the Associated Professional Sleep Societies. The workshop brought together experts in consumer sleep technologies and medical devices, sleep and circadian physiology, clinical translational research, and clinical practice. The goals of the workshop were: (1) characterize the term "wearable" for use in sleep and circadian science and identify relevant sleep and circadian metrics for wearables to measure; (2) assess the current use of wearables in sleep and circadian science; (3) identify current barriers for applying wearables to sleep and circadian science; and (4) identify goals and opportunities for wearables to advance sleep and circadian science. For the purposes of biomarker development in the sleep and circadian fields, the workshop included the terms "wearables," "nearables," and "ingestibles." Given the state of the current science and technology, the limited validation of wearable devices against gold standard measurements is the primary factor limiting large-scale use of wearable technologies for sleep and circadian research. As such, the workshop committee proposed a set of best practices for validation studies and guidelines regarding how to choose a wearable device for research and clinical use. To complement validation studies, the workshop committee recommends the development of a public data repository for wearable data. Finally, sleep and circadian scientists must actively engage in the development and use of wearable devices to maintain the rigor of scientific findings and public health messages based on wearable technology.

The effects of COVID-19 quarantine on eating and sleeping behaviors.

Abstract: Since the beginning of the pandemic, the population has been exposed to a substantial period of social isolation, which leads to anxiety, fear, and metabolic and immune impairments. Purpose: Considering that sleep restriction influences eating behavior, we highlight that changes in it may occur during the COVID-19 quarantine. Alterations in feeding time can uncouple the body clocks, leading to circadian misalignment and consequently to a disruption in homeostasis and disturbances in many metabolic functions. Method: Narrative review. Results: Do not apply. Conclusion: The increase of body weight is related to increased food intake in response to mental stress and more time spent at home, increased opportunity to feed, and increased visual and olfactory stimulation to eat, which represents a potential risk of overfeeding nowadays. In this article, we postulate that the unusual lifestyle imposed by the COVID-19 quarantine may induce a circadian misalignment, which is capable to induce alterations on eating and sleep behaviors.

Trait-like vulnerability of higher-order cognition and ability to maintain wakefulness during combined sleep restriction and circadian misalignment.

STUDY OBJECTIVES: Determine stability of individual differences in executive function, cognitive processing speed, selective visual attention, and maintenance of wakefulness during simulated sustained operations with combined sleep restriction and circadian misalignment. METHODS: Twenty healthy adults (eight female), aged 25.7 (±4.2 SD), body mass index (BMI) 22.3 (±2.1) kg/m2 completed an 18-day protocol twice. Participants maintained habitual self-selected 8-hour sleep schedules for 2 weeks at home prior to a 4-day laboratory visit that included one sleep opportunity per day: 8 hours on night 1, 3 hours on night 2, and 3 hours on mornings 3 and 4. After 3 days of unscheduled sleep at home, participants repeated the entire protocol. Stability and task dependency of individual differences in performance were quantified by intra-class correlation coefficients (ICC) and Kendall's Tau, respectively. RESULTS: Performance on Stroop, Visual Search, and the Maintenance of Wakefulness Test were highly consistent within individuals during combined sleep restriction and circadian misalignment. Individual differences were trait-like as indicated by ICCs (0.54-0.96) classified according to standard criteria as moderate to almost perfect. Individual differences on other performance tasks commonly reported in sleep studies showed fair to almost perfect ICCs (0.22-0.94). Kendall's rank correlations showed that individual vulnerability to sleep restriction and circadian misalignment varied by task and by metric within a task. CONCLUSIONS: Consistent vulnerability of higher-order cognition and maintenance of wakefulness to combined sleep restriction and circadian misalignment has implications for the development of precision countermeasure strategies for workers performing safety-critical tasks, e.g. military, police, health care workers and emergency responders.