Circadian Rhythm

People differ in chronotype - whether they function best in the morning ("larks") or the evening ("owls"). This study asks whether the match or mismatch between a person's chronotype and the time of day at which they are tested changes how they perceive time. Healthy morning-type and evening-type adults at three sites (Aarhus, Denmark; Changzhou, China; and Hong Kong) complete the same battery of perception and cognition tasks twice - once in the early morning (about 08:00) and once late in the evening (about 22:00), in counterbalanced order. The primary outcome is the accuracy (signed bias) of time-perception judgements; the key comparison is the interaction between chronotype and time of day (the "synchrony effect"). Secondary measures include timing precision, the subjective passage of time, sleepiness, mood, colour perception (with and without blue-blocking glasses) and perceptual decision-making. By testing the same protocol across three cultures and latitudes, the study examines whether circadian match/mismatch effects on temporal cognition generalise across populations.

Depression is a leading cause of global disease burden, poor quality of life, disability and suicide, and commonly occurs in adolescence and early adulthood. Insomnia and circadian factors were regarded as potential targets for preventing worsening of depressive symptoms. Additionally, digital insomnia treatment reduces depressive symptoms but is insufficient for individuals with an evening chronotype. Circadian intervention is an adjunctive treatment for sleep disturbance and depression, but is often overlooked. In this study, we aim to evaluate the effect of guided digital insomnia and circadian intervention (dCBT-I + dCI) in reducing depressive symptoms in college students with insomnia and an evening chronotype compared with digital insomnia intervention alone (dCBT-I) and a health education group (dHE). We also aim to develop and evaluate multimodal prediction models to identify individuals who are more or less likely to respond to the interventions, using clinical, behavioral, circadian, and digital engagement data.

Obstructive Sleep Apnea Syndrome (OSA) is a condition characterized by repeated pauses or reductions in breathing during sleep, which can negatively affect sleep quality, daytime functioning, and physical capacity. Although regular exercise is known to have beneficial effects in OSA, the effects of different exercise approaches on circadian rhythm and functional capacity have not been sufficiently investigated.The primary aim of this study is to compare the effects of exercise snacking and aerobic exercise on circadian rhythm and functional capacity in individuals with OSA, in comparison with a control group. The secondary aim is to evaluate the effects of these exercise interventions on peripheral muscle strength, fatigue level, body composition, quality of life, and physical activity level.Participants will be randomly assigned to three groups: an aerobic exercise group, an exercise snacking group, and a control group. While the exercise groups will follow their respective intervention programs, the control group will continue their routine treatment.This study aims to answer whether exercise snacking, which consists of short bouts of exercise distributed throughout the day, may be an alternative or complementary approach to traditional aerobic exercise in individuals with OSA. In addition, this study aims to be the first randomized controlled trial evaluating the effects of exercise snacking on circadian rhythm and functional capacity in individuals with OSA.

The proposed project aims to disentangle the impact of evening light exposure emitted from tablet devices from the impact of arousing media content on children's sleep regulation, circadian physiology and next-day emotion regulation and executive functioning.

This study, in a quasi-experimental matched two-group pre-post design, investigates the effect of serial water-filtered whole-body hyperthermia on circadian core body temperature, the somatosensory system (nociception) and the movement evoked pain in healthy and patients with chronic primary pain (e.g., fibromyalgia). The intervention lasts 3 weeks with two treatment sessions per week.

This will be a single-center, prospective observational study designed to evaluate the feasibility and accuracy of a new wearable device for non-invasive continuous monitoring of physiological signals to derive circadian rhythm. Melatonin sampling will be included for comparison against wearable-derived measures

The purpose of this study is to examine the impact of timed cortisol release or differently timed cortisol rhythms on insulin resistance in both men and women undergoing sleep restriction. Chronic sleep loss is highly prevalent, affecting 1 in 3 adults in the US. Chronic sleep loss causes stress which induces insulin resistance and leads to obesity and type 2 diabetes. Many factors contribute to sleep loss including shift work, environmental disturbances, sleep/circadian disorders and comorbid medical and mental health conditions. Sleep loss increases the stress hormone cortisol in the evening and decreases daytime testosterone. Examining these hormones in a controlled laboratory environment under different sleep schedules may help researchers find solutions for adults experiencing negative health consequences related to chronic sleep loss.

The goal of this clinical trial is to examine how daily behavioral patterns in early pregnancy, including sleep, physical activity, and meal timing, influence continuous glucose dynamics and subsequent risk of gestational diabetes mellitus (GDM) in pregnant women without pre-existing diabetes. The main questions it aims to answer are: 1. Do early-pregnancy chronobehavioral patterns (e.g., irregular sleep, night eating, and unstable rest-activity rhythms) relate to continuous glucose patterns measured using continuous glucose monitoring (CGM)? 2. Can early behavioral and CGM-derived measures predict glucose regulation and metabolic outcomes later in pregnancy (24-28 weeks)? 3. Does real-time self-monitoring using wearable devices and food logging improve glycemic outcomes compared to usual care? This study is a prospective, nested randomized pilot trial embedded within the ongoing Towards Optimal Fertility, Fathering and Fatherhood studY (TOFFFY) cohort (NCT06293235) at KK Women's and Children's Hospital, Singapore. A total of 140 pregnant women without pre-existing diabetes, recruited at ≤13 weeks gestation, will be randomized in a 1:1 ratio to either a pilot arm (wearable-based self-monitoring) or a control arm (usual care). Participants in the pilot arm (n=70) will undergo intensive behavioral and metabolic monitoring over a 14-day period in early pregnancy, including continuous glucose monitoring using a CGM device, wrist actigraphy to assess sleep-wake and rest-activity patterns, and an AI-supported mobile application to record meal timing and dietary intake. Participants will have real-time access to their glucose data and behavioral feedback, enabling self-monitoring and potential behavioral adjustments.

This study investigates whether the timing of feeding expressed breast milk influences infant sleep and circadian (day-night) development in preterm infants. In early life, infants produce very little of the hormone melatonin, which plays a key role in regulating sleep and circadian rhythms. Breast milk naturally contains melatonin, and its levels vary across the day, with higher concentrations at night. This variation may provide important biological signals that help infants develop healthy sleep-wake patterns. However, expressed breast milk is often fed without considering the time it was expressed. This may disrupt the transfer of circadian signals from mother to infant. The aim of this randomised controlled trial is to determine whether feeding expressed breast milk according to the time of expression (e.g. giving night-time milk at night) improves sleep consolidation and circadian development compared with usual feeding practices. A total of 200 preterm infants born between 32+0 and 36+6 weeks' gestation who are receiving expressed breast milk will be enrolled and randomly assigned to one of two groups: Intervention group: preterm infants receive expressed breast milk matched to the time of day it was expressed (day, evening or night) Control group: preterm infants receive expressed breast milk without regard to timing (usual practice) The main outcome is sleep consolidation at 6 months of age, measured objectively using actigraphy (a small wearable device that records sleep and activity). Additional outcomes include sleep patterns over time, circadian development, melatonin exposure, gut microbiota composition, and clinical outcomes such as infections and neurodevelopment. The intervention does not involve any medication and uses the infant's usual nutrition. Risks are minimal and mainly relate to the additional effort required for milk labelling and timing. This study will provide evidence on whether a simple, low-risk change in feeding practice can support infant sleep and early-life circadian development, with potential benefits for child health and family well-being.

The goal of this study is to learn how cannabis use and discontinuation affect sleep, circadian rhythms, and sensitivity to light. The main questions it aims to answer are: 1. Does cannabis use and discontinuation impact sleep drive? 2. Does cannabis use and discontinuation impact light sensitivity and circadian phase?

The aim of this study is to determine the effect of Progressive Relaxation Exercise (PGE) applied according to the circadian rhythms of hemodialysis (HD) patients on symptom management, sleep quality, comfort and mental well-being levels and to examine the experiences of HD patients regarding PGE application. A sequential mixed method research design will be used in the study. The quantitative part of the study was planned as a randomized controlled double-blind experimental study. The qualitative part will be conducted as a qualitative research to be carried out with individual in-depth interview method in order to examine the opinions of the individuals in the intervention group regarding the 8-week PGE applied according to the circadian rhythm. In the collection of research data, the Introductory Information Form, Morningness-Eveningness Questionnaire (MEQ), Dialysis Symptom Index, Hemodialysis Comfort Scale - Version II, Pittsburg Sleep Quality Index (PSQI), Warwick-Edinburgh Mental Well-Being Scale (WEMIOÖ), Individual Follow-up Form, Progressive Relaxation Exercise Application Guideline (PGEUY) and In-Depth Interview Form with Individuals in the Intervention Group will be used.

The prevalence of sleep disturbance among postmenopausal women has been reported to reach 51.6%. Epidemiological studies consistently show that the incidence of sleep disorders increases with age and menopausal transition. Compared with premenopausal women, postmenopausal women demonstrate reduced circadian rhythm stability and a higher prevalence of sleep disturbance. In this population, levels of melatonin, total sleep time, sleep latency, N3 stage sleep, and the circadian amplitude of alertness are all diminished. Sleep disturbance can adversely affect both the mental and physical health of women and significantly impair their social functioning. Poor sleep is associated with decreased cognitive performance and heightened emotional distress, contributing to diminished quality of life. Circadian rhythms are endogenous physiological and behavioral cycles that oscillate over approximately 24 hours, governing critical processes such as sleep-wake cycles, hormonal fluctuations (e.g., cortisol and melatonin). These rhythms are regulated by the suprachiasmatic nucleus (SCN). Disruptions in circadian rhythms have been associated with sleep disturbances. Esketamine is the S (+) enantiomer of ketamine and has a higher affinity for the NMDA receptor than the R-enantiomer. Previous studies have demonstrated that intraoperative administration of esketamine can improve postoperative sleep quality and reduce the incidence of postoperative sleep disturbances, through its antidepressant efficacy, anti-inflammatory properties, analgesic efficacy, neurocognitive and anxiolytic effects. However, few studies have investigated whether esketamine can regulate perioperative circadian rhythms and subsequently affect sleep, especially in postmenopausal women. The objective of this multi-center, prospective, randomized controlled clinical trial is to investigate the effects of esketamine on postoperative sleep in postmenopausal women.

Taiwan is becoming a super-aged society, and more older adults are living with Alzheimer's disease. Many people with Alzheimer's experience behavioral and psychological symptoms, such as agitation, sleep problems, or mood changes. These symptoms often lower their quality of life and increase stress for their family caregivers. This study will test two wearable devices in people with Alzheimer's and their caregivers. One device, called Geneactiv, is a wristwatch that tracks daily activity and sleep. The other device, called Re-Timer, is a light therapy eyewear that may help improve sleep and mood. Researchers will look at how easy the devices are to use, whether participants are willing to wear them for several weeks, and whether the light therapy helps reduce sleep problems or caregiver stress. The study will also compare information from questionnaires with information collected by the devices. The results may help researchers design future studies using wearable tools to better support people living with dementia and their caregivers.

This study is designed to determine whether time-of-day and menstrual cycle phase influence athletic performance and is expected to contribute valuable insight into how both time-of-day, and hormonal factors can influence performance and expand existing research. This study aims to support more inclusive, effective and personalised approaches to training and competition schedules for female athletes. The study will involve two testing days that require a participant to complete a compilation of tests at 07:00, 12:00 and 18:00 hours. The testing days will be arranged for when a participant is in phase 1 (lowest levels of progesterone in the menstrual cycle) and phase 4 (highest level of progesterone in the menstrual cycle). The tests will examine a participant's executive function and physical strength. This study will aim to recruit thirty 18-30-year-old females from Lancaster University who identify with a sport that they train \~3 times a week for with a purpose to compete. The females recruited must have a regular menstrual cycle and no history of sleep disorders. Aim: To investigate the effects of time-of-day and menstrual cycle phase (low and high progesterone levels) on executive function and strength in females. Objectives: 1. To determine the effects of time-of-day on executive function and strength tests. 2. To determine the effects of menstrual cycle phase on executive function and strength tests. 3. To examine if there is an interaction between time-of-day and menstrual cycle phase on executive function and strength tests.

Sleep and metabolism are closely interconnected, and emerging evidence suggests that dietary composition may influence both sleep quality and key physiological functions such as glucose regulation, cardiovascular activity, and hormonal signaling. This study aims to investigate how a Western-style unhealthy diet versus a healthier, fiber-rich diet affects objective and subjective sleep measures, 24-hour physiological parameters, and a range of biomarkers related to cardiometabolic, neurodegenerative, and gut microbial function.

This proposed study will be a longitudinal follow-up study of a case-control study of 160 participants (CREC Ref: 2023.234). This study aims to follow up on the trajectory of depression and rest-activity rhythm (RAR) disruptions, as well as examine their association over time. The investigators aim to identify distinctive RAR profiles of MDD using the data from the original project and hypothesize that two or more groups will be identified based on individual RAR variables using cluster analysis. The investigators hypothesize that significant differences in depressive symptom severity, sleep quality, and other outcome measures collected in this follow-up will be found between the clustered groups. Individuals exhibiting the most disrupted RAR profiles are hypothesized to have the greatest deterioration in depression symptom severity and other outcome measures. The investigators also hypothesize that people persisting with MDD will exhibit greater disruptions in RAR compared to those without MDD at the follow-up. Furthermore, the investigators will examine whether individual RAR parameters are longitudinally associated with changes in depression symptom severity and other outcome measures.

Sleep is an important factor for overall health. This study will see how different light exposure patterns and food intake impact a person's metabolism (how the body breaks down food) when sleeping is reduced. Participants will attend 6 to 8 in-person visits to the study clinic, including three overnight stays. People will complete surveys and medical tests. The study will last about 4 to 6 months.

The aim of this project is to evaluate the effect of a dynamic light in order to improve the circadian rhythm, provide a better sleep and well-being, and in the long run an improved recovery. The primary question is whether dynamic artificial light with circadian stimulus can affect the circadian rhythm. The secondary question is whether this also provides better sleep and well-being. The group that is particularly interesting to study is a geriatric population that is more sensitive to circadian rhythm disorders, sleep disorders and confusion in connection with hospitalization and that can be of particular benefit from this intervention.

This randomized controlled trial will evaluate the impact of chrono-nutrition, a dietary approach that aligns meal timing with the body's circadian rhythms, on weight change, metabolic outcomes, appetite, and gut microbiota in post-bariatric surgery patients. A total of 246 adults who underwent sleeve gastrectomy at least six months earlier will be enrolled at King Saud Medical City. Participants will be randomized to receive either standard post-bariatric nutritional care or personalized chrono-nutrition based on individual chronotype. Outcomes include weight change, metabolic biomarkers, dietary behaviors, sleep patterns, and gut microbiota composition. The study aims to determine whether integrating chrono-nutrition into post-bariatric follow-up can enhance metabolic health and improve long-term health.

This study examines how a person's natural daily rhythm ("chronotype") affects the way time is experienced and judged. Healthy Danish-speaking adults (23-45 years) who are clearly morning-type or evening-type will complete two lab sessions in a crossover design: one at their preferred time of day (e.g., morning for morning-types) and one at the opposite time (misaligned). In each session, participants do brief computerized tasks that measure time estimation/production, vigilance (psychomotor vigilance task), decision-making, and responses to social information, plus simple color-vision tasks. Short questionnaires about sleepiness, mood, fatigue, and the subjective "passage of time" are collected before, during, and after testing. A subset will wear a wrist actigraphy device for one week beforehand to characterize sleep-wake patterns. Testing is conducted under standardized lab conditions with scheduled breaks. The main goal is to determine whether time judgments and vigilance are less accurate during the misaligned session and whether decision-making and social responses also vary with circadian timing. Risks are minimal and mainly relate to temporary tiredness when tested at a non-preferred time; participants may stop at any time. Participation is voluntary. Data are pseudonymized and handled under GDPR. Participants receive DKK 300 after completing both sessions (pro-rated if they withdraw early). Results will be published regardless of outcome, and de-identified data/code will be shared after publication.This study examines how a person's natural daily rhythm ("chronotype") affects the way time is experienced and judged. Healthy Danish-speaking adults (23-45 years) who are clearly morning-type or evening-type will complete two lab sessions in a crossover design: one at their preferred time of day (e.g., morning for morning-types) and one at the opposite time (misaligned). In each session, participants do brief computerized tasks that measure time estimation/production, vigilance (psychomotor vigilance task), decision-making, and responses to social information, plus simple color-vision tasks. Short questionnaires about sleepiness, mood, fatigue, and the subjective "passage of time" are collected before, during, and after testing. A subset will wear a wrist actigraphy device for one week beforehand to characterize sleep-wake patterns. Testing is conducted under standardized lab conditions with scheduled breaks. The main goal is to determine whether time judgments and vigilance are less accurate during the misaligned session and whether decision-making and social responses also vary with circadian timing. Risks are minimal and mainly relate to temporary tiredness when tested at a non-preferred time; participants may stop at any time. Participation is voluntary. Data are pseudonymized and handled under GDPR. Participants receive DKK 300 after completing both sessions (pro-rated if they withdraw early). Results will be published regardless of outcome, and de-identified data/code will be shared after publication.

This study examines how the internal body clock (circadian rhythms) influences the way healthy adults experience time, think, and feel when they stay awake for an extended period. Participants will spend about 36 hours in a controlled sleep laboratory while remaining awake the entire time. Light, posture, food intake, and activity are kept as constant as possible (a "constant routine") so that changes over time mainly reflect the body's internal clock and increasing sleepiness, rather than changes in the environment. Every two hours, participants complete a brief test battery that includes ratings of sleepiness and mood, a reaction-time task, and short tasks that assess how fast or slow time seems to pass, how accurately they can estimate time intervals, how they respond to simple decisions, and how they judge colours. Saliva samples are collected repeatedly to measure melatonin, a hormone that indicates circadian phase. By comparing changes in behaviour, perception, and melatonin levels across the 36-hour wake period, the study aims to identify when during the circadian cycle people are most vulnerable to distortions in time perception and reduced alertness. The findings may help improve scheduling of shift work and other activities that require sustained wakefulness.

The goal of this randomized crossover clinical trial is to investigate whether exercise-induced hypoalgesia (EIH) is influenced by circadian rhythm in healthy adults aged 18-40 years. The main questions it aims to answer are: * Does the time of day (morning vs. evening) influence changes in pain perception following exercise? * Do chronotype, sex, or stimulation site (bony vs. muscular) alter the magnitude of this effect? Participants will: * Complete questionnaires * Undergo quantitative sensory testing * Attend both morning and evening sessions in randomized crossover order

This study examines whether doing moderate resistance exercises in the morning can improve sleep quality and well-being in young adults. Participants with different daily activity patterns (morning or evening types) will take part in an 8-week online exercise program. The study will compare how exercise affects sleep, mood, and daily rhythm across these groups.

The goal of this study is to identify the effects of sleep regularity on cardiovascular regulatory mechanisms. The investigators are hoping to discover if improving the regularity of sleep timing will improve metabolic and vascular health markers. The protocol is a 12-week prospective cohort study that includes both field and in-laboratory data collection in ostensibly healthy male and female adults, aged 18-40years. We will also have a sub-group of individuals with chronic pain to examine the effects of sleep regularity on pain outcomes.

The goals of this study are to uncover the influence of diet on the human circadian timing system. The protocol is a 46-day (28 outpatient days, 18 inpatient days over two 9 day visits) randomized cross-over study designed to elucidate the speed of entrainment in response to a high-fat diet.