Chronotype

This observational behavioural study examines whether individual differences in sleep quality, sleep timing, and chronotype are associated with prosocial allocation decisions in adults. Participants will complete self-report sleep and circadian questionnaires, including the Pittsburgh Sleep Quality Index and the Munich Chronotype Questionnaire, a 7-day sleep diary, and a brief computer-based Dictator Game allocation task. The study does not involve sleep deprivation, sleep restriction, treatment, clinical diagnosis, medication, or medical devices. Participants will not be asked to change their sleep schedule. The Dictator Game decisions are hypothetical and do not affect participants' compensation. The study is intended to describe associations between naturally occurring sleep-related individual differences and behavioural allocation choices, not to diagnose or treat sleep or mental health conditions.

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.

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.

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.