Actively Recruiting
Circadian Rhythms and Time Perception in Healthy Adults During Constant Wakefulness
Led by University of Aarhus · Updated on 2025-12-22
30
Participants Needed
1
Research Sites
107 weeks
Total Duration
On this page
Sponsors
U
University of Aarhus
Lead Sponsor
I
Independent Research Fund Denmark
Collaborating Sponsor
AI-Summary
What this Trial Is About
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
Official Title
Circadian Rhythms and Time Perception in Healthy Adults During Constant Wakefulness
Who Can Participate
Eligibility Criteria
You may qualify if you...
- 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 confirmed by medical history and screening.
- Regular sleep-wake schedule for at least 4 weeks prior (about 6.5-9 hours per night, usual sleep time between 22:00-01:00 and 06:00-09:00).
- Body mass index approximately between 18.5 and 30 kg/m�b2 if required by the study physician.
- No regular night 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.
- Willingness to abstain from caffeine, nicotine, alcohol, and recreational drugs during specified washout periods before and during the study.
- For those who can become pregnant: negative pregnancy test at screening/arrival and agreement to use reliable contraception during participation.
You will not qualify if you...
- Any known or suspected major sleep disorder (e.g., insomnia, obstructive sleep apnea, restless legs syndrome, narcolepsy).
- Current or past major psychiatric or neurological disorders unless mild, stable, and approved by the study physician.
- Chronic medical conditions that could worsen with prolonged wakefulness or affect results, such as significant cardiovascular disease, uncontrolled hypertension, diabetes, severe respiratory disease, or serious illness.
- Regular use of medications or supplements affecting sleep, circadian rhythms, melatonin, alertness, or mood, unless safely washed out and approved.
- High caffeine intake (>400 mg/day) or nicotine dependence if unable or unwilling to abstain during required washout.
- Current harmful alcohol use, substance use disorder, or frequent recreational drug use.
- Pregnancy or breastfeeding.
- Previous severe adverse reaction to sleep deprivation or similar protocols.
- Claustrophobia or inability to tolerate prolonged stays in a controlled lab setting.
- Any condition that makes participation unsafe, interferes with the 36-hour wake protocol, or affects data quality (e.g., inability to stay awake, fear of needles or saliva sampling, or inability to follow study restrictions).
AI-Screening
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Trial Site Locations
Total: 1 location
1
Aarhus University, Department of Psychology and Behavioural Sciences
Aarhus, Denmark, 8000
Actively Recruiting
Research Team
A
Ali Amidi, PhD
CONTACT
C
Cehao Yu, PhD
CONTACT
How is the study designed?
Study Type
INTERVENTIONAL
Masking
NONE
Allocation
NA
Model
SINGLE_GROUP
Primary Purpose
BASIC_SCIENCE
Number of Arms
1
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