Circadian Rhythms and Time Perception in Healthy Adults During Constant Wakefulness

NCT07294781 | Recruiting DMC

• 2 other identifiers: 1-10-72-117-2510.46540/4256-00108B
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Circadian Rhythm; Sleep Deprivation; Healthy Volunteers; Time Perception

Keywords

Circadian rhythms; Constant routine; Extended wakefulness; Sleep loss; Time perception; Subjective time; Psychomotor vigilance task; Dim light melatonin onset; Healthy adults

Outcome Measures

Primary Outcomes (1)

• Time-Interval Production Error Across 36-Hour Constant Routine

  Mean absolute error (in seconds) between produced and target time intervals on a time-production task. Participants are asked to produce predefined intervals (e.g., several seconds) without external timing cues. For each 2-hour block, time-production error is averaged across trials; analyses model changes in error across circadian phase and hours awake during the 36-hour constant routine.

  From the beginning of the constant-routine wakefulness session through 36 hours of continuous wakefulness (time-production task completed every 2 hours).

Secondary Outcomes (3)

• Subjective Passage-of-Time Ratings Across 36-Hour Constant Routine

  From the beginning of the constant-routine wakefulness session through 36 hours of continuous wakefulness (passage-of-time ratings completed every 2 hours).

• Psychomotor Vigilance Task (PVT) Median Reaction Time

  From the beginning of the constant-routine wakefulness session through 36 hours of continuous wakefulness (PVT completed every 2 hours).

• Dim Light Melatonin Onset (DLMO) Timing

  During the 36-hour constant-routine wakefulness session (salivary melatonin sampled approximately hourly).

Study Arms (1)

Constant Routine Wakefulness

OTHER

Single-group 36-hour constant-routine protocol with continuous wakefulness. Participants remain in a controlled laboratory environment under low, constant light, with restricted posture and activity, and receive small isocaloric snacks at fixed intervals. Every two hours they complete a standardised test battery assessing time perception, vigilance, mood, and related cognitive and perceptual outcomes.

Behavioral: Constant Routine Wakefulness

Interventions

Constant Routine Wakefulness BEHAVIORAL

Behavioral intervention consisting of approximately 36 hours of continuous wakefulness under constant-routine conditions. Environmental factors (light level, temperature, noise) are held as constant as feasible; posture and activity are standardised; and participants receive small, isocaloric snacks at regular intervals. A repeated cognitive and perceptual test battery is administered every two hours to assess time perception, vigilance, mood, and related functions across the circadian cycle.

Constant Routine Wakefulness

Eligibility Criteria

• Age: 23 Years - 45 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Age 23 to 45 years.
• Able and willing to provide written informed consent.
• Fluent in Danish and able to understand study procedures and instructions.
• Generally healthy, as assessed by medical history, screening questionnaires, and basic clinical measures (e.g., blood pressure, heart rate).
• Self-reported regular sleep-wake schedule for at least 4 weeks prior to the laboratory visit (typically 6.5-9 hours of sleep per night, with usual sleep period between approximately 22:00-01:00 and 06:00-09:00).
• Body mass index (BMI) within a non-extreme range (for example, approximately 18.5-30 kg/m²), if required by the study physician.
• No regular night work or rotating shift work during the 3 months before participation.
• No travel across more than 2 time zones in the 2 months before the constant-routine session.
• Willing to abstain from caffeine, nicotine, alcohol, and recreational drugs for the specified washout periods before and during the 36-hour constant-routine session.
• For participants who can become pregnant: negative pregnancy test at screening/arrival and agreement to use reliable contraception for the duration of participation.

You may not qualify if:

• Any known or suspected major sleep disorder (e.g., insomnia disorder, obstructive sleep apnoea, restless legs syndrome, narcolepsy), based on self-report or prior diagnosis.
• Current or past major psychiatric or neurological disorders (e.g., major depressive disorder, bipolar disorder, psychotic disorders, epilepsy), unless considered mild and stable and explicitly approved by the study physician.
• Chronic medical conditions that could be worsened by prolonged wakefulness or that might confound outcome measures, such as significant cardiovascular disease, uncontrolled hypertension, diabetes mellitus, severe respiratory disease, or other serious systemic illness.
• Regular use of medications or supplements that may affect sleep, circadian rhythms, melatonin secretion, alertness, or mood (e.g., hypnotics, sedative-hypnotics, melatonin, stimulants, certain antidepressants or beta-blockers), unless a safe washout is possible and approved by the study physician.
• High habitual caffeine intake (for example, \>400 mg/day) or nicotine dependence if the participant is unable or unwilling to abstain for the required washout periods.
• Current harmful alcohol use or substance use disorder, or frequent use of recreational drugs.
• Pregnancy or breastfeeding.
• Previous severe adverse reaction to sleep deprivation, extended wakefulness, or similar laboratory protocols.
• Claustrophobia or inability to tolerate prolonged stays in a controlled laboratory environment.
• Any condition or circumstance that, in the judgement of the investigators, would make participation unsafe, interfere with the 36-hour wakefulness protocol, or compromise data quality (e.g., inability to remain awake despite support, strong fear of needles or saliva sampling, or inability to comply with study restrictions).

Sponsors & Collaborators

• University of Aarhus: lead
• Independent Research Fund Denmark: collaborator

Study Sites (1)

Aarhus University, Department of Psychology and Behavioural Sciences

Aarhus, 8000, Denmark

RECRUITING

Related Publications (3)

• Kuriyama K, Uchiyama M, Suzuki H, Tagaya H, Ozaki A, Aritake S, Shibui K, Xin T, Lan L, Kamei Y, Takahashi K. Diurnal fluctuation of time perception under 30-h sustained wakefulness. Neurosci Res. 2005 Oct;53(2):123-8. doi: 10.1016/j.neures.2005.06.006.

  PMID: 16039739 RESULT

• Yu C, Van Zuijlen MJP, Spoiala C, Pont SC, Wijntjes MWA, Hurlbert A. Time-of-day perception in paintings. J Vis. 2024 Jan 2;24(1):1. doi: 10.1167/jov.24.1.1.

  PMID: 38165679 RESULT

• Hurlbert A, Yu C. Seeing the Light: Perception and Discrimination of Illumination Color. Annu Rev Vis Sci. 2025 Sep;11(1):267-301. doi: 10.1146/annurev-vision-121423-013755. Epub 2025 Aug 5.

  PMID: 40763251 RESULT

Related Links

• Sleep \& Circadian Psychology Research Unit - Aarhus University (information on research in sleep, circadian rhythms, and time perception)

MeSH Terms

Conditions

Sleep Deprivation

Condition Hierarchy (Ancestors)

Dyssomnias; Sleep Wake Disorders; Nervous System Diseases; Neurologic Manifestations; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Mental Disorders

Central Study Contacts

Ali Amidi, PhD

CONTACT

45 87165305; ali@psy.au.dk

Cehao Yu, PhD

CONTACT

cehao.yu@psy.au.dk

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Masking Details: Open-label, single-group basic science study; no masking used.
• Purpose: BASIC SCIENCE
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: All participants complete a single 36-hour constant-routine protocol with continuous wakefulness under controlled environmental conditions.

Study Record Dates

• First Submitted: December 8, 2025
• First Posted: December 19, 2025
• Study Start: December 5, 2025
• Primary Completion (Estimated): December 30, 2027
• Study Completion (Estimated): December 30, 2027
• Last Updated: December 22, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: De-identified individual participant data and supporting documents will be made available beginning within 12 months after publication of the main results article and will remain available for at least 5 years thereafter.
• Access Criteria: De-identified individual participant data (IPD), together with the study protocol, statistical analysis plan, and analytic code, will be available to qualified researchers affiliated with recognised research institutions who submit a methodologically sound proposal and obtain any required ethical or institutional approvals. Requests should describe the planned analyses and data needed. Approved requesters will sign a data use agreement prohibiting re-identification of participants and requiring appropriate data security. Data will be shared via secure transfer or a controlled-access repository approved by Aarhus University.

Locations

DK (1)