Circadian SystemDayCiSNCT05513547
Beneficial Effects of Daytime Light Exposure and Physical Activity on the Human Circadian Clock and Sleep
A study testing LE protocol 1: exposure to artificial light, LE protocol 2: natural daylight and LE protocol 3: natural daylight with reduced short-wavelength proportions in people with Circadian System, run by University Hospital, Basel, Switzerland at 1 site in Switzerland.
Trial summary
This study is to examine the circadian phase-shifting effects of daylight and physical activity (primary endpoint: shift in dim-light melatonin onset (DLMO)) as well as their effects on sleep the ensuing night and analyzes how different spectral characteristics of daylight and physical activity affect the biological… Read more about this study
- Who is it for?
- Ages 18 to 35 yearsHealthy volunteers can take part
- Conditions the study is for
- Circadian System
- What is being tested?
- LE protocol 1: exposure to artificial light, LE protocol 2: natural daylight and LE protocol 3: natural daylight with reduced short-wavelength proportions
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 51 participants
- Where
- 1 siteSwitzerland
- Study dates
- 27 Apr 2023to 12 Sep 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 35 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Age: 18-35 years
- Body Mass Index: 18.5-24.9 (i.e., normal weight according to World Health Organization (WHO) criteria)
- Moderate cardiorespiratory fitness levels, moderate level of endurance training according to the category "moderate physical activity" (category 2) of the International Physical Activity Questionnaire (IPAQ) short form
- Informed consent as documented by signature of the participant
Who cannot join
- Self-reported pregnancy
- Investigator's family members, employees, or other dependent persons
- Chronic or debilitating medical (including psychiatric) conditions; normal state of health will be established on the basis of questionnaires and the examination by the physician in charge. Illnesses that would be a reason for exclusion are:
- Sleep disorders: Narcolepsy, sleep apnea (apnea index > 10), periodic limb movements (PLM index > 15), insomnia (polygraphically recorded sleep efficiency < 70% or Pittsburgh Sleep Quality Index (PSQI) index > 5), hypersomnia
- Chronobiological disorders: hypernychthemeral sleep-wake cycle, delayed or advanced sleep phase syndrome
- Psychiatric disorders
Show all 16Show fewer
- Somatic diseases: cardiovascular, respiratory, gastrointestinal, haemopoietic, visual and immune system diseases, neurological disorders, infectious diseases, allergies (e.g., skin allergies, acute hay fever), thrombocytopenia or other dysfunctions of blood platelets
- Drug use: volunteers must not consume any drugs (including nicotine and alcohol) for the entire duration of the study with no history of drug or alcohol dependency. This will be ensured by the use of a urine multi-drug screen at every experimental visit.
- Medication that could affect outcome parameters
- Shift work < 3 months prior to study intake
- Transmeridian travel (> 2 time zones) < 1 month prior to study intake
- Extreme chronotype (Munich Chronotype Questionnaire [MCTQ] <2 or >7)
- Extremely long/short sleep duration (subjective sleep duration on workdays outside 6-10h according to the MCTQ)
- Abnormal colour vision, vision disorders (other than e.g., mild myopia corrected with contact lenses)
- Inability to understand and/or follow procedures
- Non-adherence to the circadian stabilization protocol during the five days prior to and between the experimental visits (deviation of >30min form scheduled times more than twice or on the day of the study visit)
Trial locations and contacts
1 site in 1 country.
Switzerland1 site
Centre for Chronobiology, Psychiatric Hospital of the University of Basel
Basel, 4002
About this study
This study is to examine the circadian phase-shifting effects of daylight and physical activity (primary endpoint: shift in dim-light melatonin onset (DLMO)) as well as their effects on sleep the ensuing night and analyzes how different spectral characteristics of daylight and physical activity affect the biological clock and sleep.
There are two types of interventions in a within-between study plan: - Within participants: light conditions will be varied during daytime in three 7-hour light exposure protocols (usual office lighting, natural daylight, natural daylight with "blue"-light filtering glasses). - Between participants: physical activity levels (rest vs. 4 hours of moderate activity, i.e., hiking) will be varied. Eligible volunteers are invited to partake in the three-week study schedule, including three experimental visits and in-between ambulatory sleep-wake and light exposure tracking. On study intake, participants are randomly assigned to either the 'hike' or 'rest' activity subgroup. The 'resting subgroup' will be allowed to study, read, etc. during the experimental conditions, whereas the 'hiking subgroup' will have 4 hours of scheduled moderate physical activity during each LE condition starting 3 hours after waking up.
Following the screening procedure and an adaptation night to screen for sleep disorders, eligible participants will be matched with a 'partner'. One will be assigned to the rest (A), the other to the hiking (B) subgroup. LE protocols within each subgroup are identical and participants from each pair will undergo all light conditions on the same day to minimize variability due to e.g., weather conditions.
Read the detailed description
While phylogenetically, life on earth has developed under the cyclic changes of sunlight and darkness, human life in modern societies is usually characterized by a markedly different light environment: spending most of the waking day indoors in relatively low light levels, whereas exposing ourselves to relatively high levels of artificial light in the evening. This decrease in day-night contrast has detrimental effects on the human circadian system and sleep. The pathways that mediate these effects have functionally been mapped using evening or nocturnal light exposure (LE). It has been shown that light with increased short-wavelength proportions suppresses melatonin, delays the biological clock, and impairs sleep. These consequences are thought to be mainly mediated by the effects of short-wavelength light on intrinsically photosensitive retinal ganglion cells (ipRGCs), which express melanopsin that has its peak spectral sensitivity at around 480nm. Little is known about the contributions of the other retinal photoreceptors, particularly the cones, which encode colour and brightness under daylight viewing conditions. Thus, the precise contributions of melanopic and photopic illuminance remain to be established. Besides the negative effects of evening artificial LE, exposure to higher levels of daylight is associated with beneficial consequences for sleep and circadian rhythms. However, also in this respect, the precise photopic and melanopic contributions remain to be established. Beyond this, daylight exposure is often confounded with physical activity, which can act as a zeitgeber itself. Specifically, physical activity in the morning and the afternoon has been shown to acutely phase-advance the biological clock and positively affect sleep. The possible contributions of an interaction with LE remain to be established. This study aims at delineating the effects of (i) photopic and melanopic illuminance during daytime LE and (ii) physical activity on the biological clock and sleep. The spectral characteristics of daytime LE will be varied in a within-subject manner in three 7-hour LE protocols. Physical activity will be varied between subjects in two subgroups (i.e., 'hike' and 'rest'). This study investigates the relative importance of daytime and its precise spectral characteristics as well as physical activity for healthy circadian rhythms and sleep.
- Conditions
- Circadian System
- Being tested
- LE protocol 1: exposure to artificial light, LE protocol 2: natural daylight, LE protocol 3: natural daylight with reduced short-wavelength proportions
- Keywords
- daytime light exposure, human circadian clock, Dim-Light Melatonin Onset (DMLO), nocturnal light exposure, intrinsically photosensitive retinal ganglion cells (ipRGCs), retinal photoreceptors, photopic illuminance, melanopic illuminance, melanopic equivalent daylight illuminance (EDI)
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
LE protocol 1: exposure to artificial lightOther
Also called P1
Participants stay in the lab with light mimicking usual office lighting. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings.
LE protocol 2: natural daylightOther
Also called P2
Participants spend the same time outdoors in natural daylight. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings.
LE protocol 3: natural daylight with reduced short-wavelength proportionsOther
Also called P3
Participants spend the same time outdoors in natural daylight wearing tinted glasses that filter out short-wavelength light proportions. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings.
| Study group | Role | What they receive |
|---|---|---|
| resting subgroup | Other | Will be allowed to engage in activities that do not require self-luminous displays (e.g., study/read, play boardgames, listen to podcasts) during the three scheduled 7-hour light exposure (LE) conditions. For 'resting' participants, the time they spend under the open sky, in the shade or half-shade, will be matched to what the 'hikers' experience. Receives: Other: LE protocol 1: exposure to artificial light; Other: LE protocol 2: natural daylight; Other: LE protocol 3: natural daylight with reduced short-wavelength proportions |
| hiking subgroup | Other | Will have 4 hours of scheduled moderate physical activity (average approx. 70-75% of maximum heart rate during each LE starting 3h after waking up to meet the circadian time when the most pronounced phase-advance is expected. The scheduled 4-hour activity will be a hike in the greater Basel area, which will cover about 12-14 km and a gain in elevation of less than 500 metres. Participants will be instructed to walk at their own speed. During protocol 1, which will take place in the lab, participants in the 'hiking' group will walk on a tiltable treadmill. Receives: Other: LE protocol 1: exposure to artificial light; Other: LE protocol 2: natural daylight; Other: LE protocol 3: natural daylight with reduced short-wavelength proportions |
What is being measured
The primary outcome is the main question the study is designed to answer.
Difference in salivary DLMO (in minutes, phase advance) between the first and the second night (Shift in dim-light melatonin onset (DLMO))
Phase shift in the dim-light melatonin onset (DLMO) due to the light exposure from evening 1 to evening 2 of each experimental visit
Measured: On the evenings of each LE protocol (from 5 hours before habitual bedtime (HBT) (every 30 minutes)) and in the mornings during the first hour after wake-up (8h later) on day 8-10, day 15-17, day 22-24.
Secondary outcomes (8)
EEG slow-wave activity (SWA) (i.e., delta power density between 0.5 and 4.5 Hz) as an indicator of sleep propensity within each NREM part of a sleep cycle
EEG SWA for each decile of the NREM part of the first non-rapid eye movement (NREM)-REM cycle will be computed. For the computation of delta power density, artefact-free data will be segmented into 2-second time bins and subjected to Fast Fourier Transformation (FFTs) yielding a frequency resolution of 0.5 Hz. Thereafter, FFT results will be averaged in the 0.5-4.5 Hz range at frontal electrodes F3, Fz, and F4 within each percentile of each NREM cycle. For each NREM cycle, the analyses will thus yield 10 measures per participant.
Measured: On day 8-10, day 15-17, day 22-24.
Change in Karolinska Sleepiness Scale (KSS) for subjective sleepiness
KSS is a single-item 9-point subjective Likert-type measurement scale for sleepiness
Measured: On the evenings of each LE protocol, from 5 hours before HBT on day 8-10, day 15-17, day 22-24.
Change in Visual Comfort Scale (VCS) for mood, visual comfort and physical well-being.
Change in Visual Comfort Scale (VCS) to assess participants' mood, visual comfort and physical well-being under the different lighting conditions
Measured: On the evenings of each LE protocol, from 5 hours before HBT on day 8-10, day 15-17, day 22-24.
Change in Psychomotor Vigilance Task (PVT) for objective alertness
Objective alertness will be measured using an acoustic version of the Psychomotor Vigilance Task (PVT). The test will run for a total of 10 min, stopping with the last response within this time frame. False starts will be coded for RTs <100 ms and lapses will be coded for RTs ≥ 2x median. After a response, the next tone will be played randomly after 2-10 s. The reaction time data will focus on mean 1/reaction time (mean 1/RT). Mean 1/RT will be calculated after the removal of false starts and lapses.
Measured: On the evenings of each LE protocol, from 5 hours before HBT on day 8-10, day 15-17, day 22-24.
Change in Self-Assessment of Sleep and Awakening Quality Scale (SSA) for subjective sleep quality
Sleep and wake episodes will be recorded using a sleep-wake diary (bedtime, lights-off, estimated sleep onset latency, number of waking up during night, number of getting up during night, wake-up time (lights-on), and getup time in the morning, type of day (work or free), activity during the day, daylight exposure, naps, time without the actimetry device, medicine, caffeine, and alcohol). Sleep quality rated on a Likert scale (1 = very poor to 8 = very good).
Measured: Throughout the three weeks of the study protocol
Change in Polysomnography (PSG)-derived sleep stages and arousals according to the AASM Manual for the Scoring of Sleep and Associated Events for objective sleep quality
Scoring of Polysomnography (PSG)-derived sleep stages
Measured: During the nights of each experimental protocol (on day 8-10, day 15-17, day 22-24).
Change in actimetry (sleep-wake schedules) measured by actimetry devices
Change in actimetry (sleep-wake schedules) by actimetry devices
Measured: Throughout the three weeks of the study protocol
Change in participants' light exposure, measured by lightweight light sensor
Ambulatory light exposure will be assessed with a lightweight light sensor
Measured: Throughout the three weeks of the study protocol
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Aug 2022
- Study start27 Apr 2023
- Primary completion12 Sep 2025
- Study completion12 Sep 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Circadian SystemStudies of the same condition, open and under way.
- More trials run by University Hospital, Basel, SwitzerlandThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Sequential
- Model description
- Sequential Bayes Factor approach: spectral characteristics of daytime LE varied in a within-subject manner in three sequential 7-hour LE protocols (P1, P2, P3). Physical activity varied between subjects in two subgroups: one 'resting' group and one 'hiking' group. The latter will hike (P2/3) or walk on a treadmill (P1) for 4 hours during LE.
- Masking
- None (open label)
- Enrolment
- 51 participants (actual)
Sponsor and investigators
- Lead sponsor
- University Hospital, Basel, Switzerland
- Sponsor type
- University, hospital or other
- Collaborators
- Swiss National Science Foundation
- Responsible party
- Sponsor
- Investigators
- Christine Blume, Dr. med., Principal investigator, Centre for Chronobiology, Psychiatric Hospital of the University of Basel
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05513547
- Sponsor's protocol ID
- 2022-01140; pk22Blume
- Acronym
- DayCiS
- Status last verified
- Sep 2025
- First submitted
- 22 Aug 2022
- Last updated
- 26 Sep 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 26 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Beneficial Effects of Daytime Light Exposure and Physical Activity on the Human Circadian Clock and Sleep
- ClinicalTrials.gov ID
- NCT05513547
- Acronym / sponsor ID
- DayCiS / 2022-01140; pk22Blume
- Conditions
- Circadian System
- Keywords
- daytime light exposure, human circadian clock, Dim-Light Melatonin Onset (DMLO), nocturnal light exposure, intrinsically photosensitive retinal ganglion cells (ipRGCs), retinal photoreceptors, photopic illuminance, melanopic illuminance
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 51 participants (actual)
- Lead sponsor
- University Hospital, Basel, SwitzerlandUniversity, hospital or other
- Collaborators
- Swiss National Science Foundation
- Study start
- 27 Apr 2023 (actual)
- Primary completion
- 12 Sep 2025 (actual)
- Study completion
- 12 Sep 2025 (actual)
- First posted
- 24 Aug 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study is to examine the circadian phase-shifting effects of daylight and physical activity (primary endpoint: shift in dim-light melatonin onset (DLMO)) as well as their effects on sleep the ensuing night and analyzes how different spectral characteristics of daylight and physical activity affect the biological clock and sleep.
There are two types of interventions in a within-between study plan: - Within participants: light conditions will be varied during daytime in three 7-hour light exposure protocols (usual office lighting, natural daylight, natural daylight with "blue"-light filtering glasses). - Between participants: physical activity levels (rest vs. 4 hours of moderate activity, i.e., hiking) will be varied. Eligible volunteers are invited to partake in the three-week study schedule, including three experimental visits and in-between ambulatory sleep-wake and light exposure tracking. On study intake, participants are randomly assigned to either the 'hike' or 'rest' activity subgroup. The 'resting subgroup' will be allowed to study, read, etc. during the experimental conditions, whereas the 'hiking subgroup' will have 4 hours of scheduled moderate physical activity during each LE condition starting 3 hours after waking up.
Following the screening procedure and an adaptation night to screen for sleep disorders, eligible participants will be matched with a 'partner'. One will be assigned to the rest (A), the other to the hiking (B) subgroup. LE protocols within each subgroup are identical and participants from each pair will undergo all light conditions on the same day to minimize variability due to e.g., weather conditions.
Detailed description
While phylogenetically, life on earth has developed under the cyclic changes of sunlight and darkness, human life in modern societies is usually characterized by a markedly different light environment: spending most of the waking day indoors in relatively low light levels, whereas exposing ourselves to relatively high levels of artificial light in the evening. This decrease in day-night contrast has detrimental effects on the human circadian system and sleep. The pathways that mediate these effects have functionally been mapped using evening or nocturnal light exposure (LE). It has been shown that light with increased short-wavelength proportions suppresses melatonin, delays the biological clock, and impairs sleep. These consequences are thought to be mainly mediated by the effects of short-wavelength light on intrinsically photosensitive retinal ganglion cells (ipRGCs), which express melanopsin that has its peak spectral sensitivity at around 480nm. Little is known about the contributions of the other retinal photoreceptors, particularly the cones, which encode colour and brightness under daylight viewing conditions. Thus, the precise contributions of melanopic and photopic illuminance remain to be established. Besides the negative effects of evening artificial LE, exposure to higher levels of daylight is associated with beneficial consequences for sleep and circadian rhythms. However, also in this respect, the precise photopic and melanopic contributions remain to be established. Beyond this, daylight exposure is often confounded with physical activity, which can act as a zeitgeber itself. Specifically, physical activity in the morning and the afternoon has been shown to acutely phase-advance the biological clock and positively affect sleep. The possible contributions of an interaction with LE remain to be established. This study aims at delineating the effects of (i) photopic and melanopic illuminance during daytime LE and (ii) physical activity on the biological clock and sleep. The spectral characteristics of daytime LE will be varied in a within-subject manner in three 7-hour LE protocols. Physical activity will be varied between subjects in two subgroups (i.e., 'hike' and 'rest'). This study investigates the relative importance of daytime and its precise spectral characteristics as well as physical activity for healthy circadian rhythms and sleep.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Sequential Bayes Factor approach: spectral characteristics of daytime LE varied in a within-subject manner in three sequential 7-hour LE protocols (P1, P2, P3). Physical activity varied between subjects in two subgroups: one 'resting' group and one 'hiking' group. The latter will hike (P2/3) or walk on a treadmill (P1) for 4 hours during LE.
| Arm | Type | Receives |
|---|---|---|
| resting subgroup | Other | Other: LE protocol 1: exposure to artificial light, Other: LE protocol 2: natural daylight, Other: LE protocol 3: natural daylight with reduced short-wavelength proportionsWill be allowed to engage in activities that do not require self-luminous displays (e.g., study/read, play boardgames, listen to podcasts) during the three scheduled 7-hour light exposure (LE) conditions. For 'resting' participants, the time they spend under the open sky, in the shade or half-shade, will be matched to what the 'hikers' experience. |
| hiking subgroup | Other | Other: LE protocol 1: exposure to artificial light, Other: LE protocol 2: natural daylight, Other: LE protocol 3: natural daylight with reduced short-wavelength proportionsWill have 4 hours of scheduled moderate physical activity (average approx. 70-75% of maximum heart rate during each LE starting 3h after waking up to meet the circadian time when the most pronounced phase-advance is expected. The scheduled 4-hour activity will be a hike in the greater Basel area, which will cover about 12-14 km and a gain in elevation of less than 500 metres. Participants will be instructed to walk at their own speed. During protocol 1, which will take place in the lab, participants in the 'hiking' group will walk on a tiltable treadmill. |
Who may qualify
- Ages
- 18 to 35 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Age: 18-35 years
- Body Mass Index: 18.5-24.9 (i.e., normal weight according to World Health Organization (WHO) criteria)
- Moderate cardiorespiratory fitness levels, moderate level of endurance training according to the category "moderate physical activity" (category 2) of the International Physical Activity Questionnaire (IPAQ) short form
- Informed consent as documented by signature of the participant
Key exclusion criteria (16 listed)
- Self-reported pregnancy
- Investigator's family members, employees, or other dependent persons
- Chronic or debilitating medical (including psychiatric) conditions; normal state of health will be established on the basis of questionnaires and the examination by the physician in charge. Illnesses that would be a reason for exclusion are:
- Drug use: volunteers must not consume any drugs (including nicotine and alcohol) for the entire duration of the study with no history of drug or alcohol dependency. This will be ensured by the use of a urine multi-drug screen at every experimental visit.
- Medication that could affect outcome parameters
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| LE protocol 1: exposure to artificial lightAlso: P1Participants stay in the lab with light mimicking usual office lighting. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings. | Other | hiking subgroup, resting subgroup |
| LE protocol 2: natural daylightAlso: P2Participants spend the same time outdoors in natural daylight. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings. | Other | hiking subgroup, resting subgroup |
| LE protocol 3: natural daylight with reduced short-wavelength proportionsAlso: P3Participants spend the same time outdoors in natural daylight wearing tinted glasses that filter out short-wavelength light proportions. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings. | Other | hiking subgroup, resting subgroup |
Primary outcome
Difference in salivary DLMO (in minutes, phase advance) between the first and the second night (Shift in dim-light melatonin onset (DLMO))
Time frame: On the evenings of each LE protocol (from 5 hours before habitual bedtime (HBT) (every 30 minutes)) and in the mornings during the first hour after wake-up (8h later) on day 8-10, day 15-17, day 22-24.
Phase shift in the dim-light melatonin onset (DLMO) due to the light exposure from evening 1 to evening 2 of each experimental visit
8 secondary outcomes
EEG slow-wave activity (SWA) (i.e., delta power density between 0.5 and 4.5 Hz) as an indicator of sleep propensity within each NREM part of a sleep cycle
Time frame: On day 8-10, day 15-17, day 22-24.
Change in Karolinska Sleepiness Scale (KSS) for subjective sleepiness
Time frame: On the evenings of each LE protocol, from 5 hours before HBT on day 8-10, day 15-17, day 22-24.
Change in Visual Comfort Scale (VCS) for mood, visual comfort and physical well-being.
Time frame: On the evenings of each LE protocol, from 5 hours before HBT on day 8-10, day 15-17, day 22-24.
Change in Psychomotor Vigilance Task (PVT) for objective alertness
Time frame: On the evenings of each LE protocol, from 5 hours before HBT on day 8-10, day 15-17, day 22-24.
Change in Self-Assessment of Sleep and Awakening Quality Scale (SSA) for subjective sleep quality
Time frame: Throughout the three weeks of the study protocol
Change in Polysomnography (PSG)-derived sleep stages and arousals according to the AASM Manual for the Scoring of Sleep and Associated Events for objective sleep quality
Time frame: During the nights of each experimental protocol (on day 8-10, day 15-17, day 22-24).
Change in actimetry (sleep-wake schedules) measured by actimetry devices
Time frame: Throughout the three weeks of the study protocol
Change in participants' light exposure, measured by lightweight light sensor
Time frame: Throughout the three weeks of the study protocol
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 26 Sep 2025.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Christine Blume, Dr. med. principal investigator
Centre for Chronobiology, Psychiatric Hospital of the University of Basel
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing LE protocol 1: exposure to artificial light, LE protocol 2: natural daylight and LE protocol 3: natural daylight with reduced short-wavelength proportions in people with Circadian System, run by University Hospital, Basel, Switzerland at 1 site in Switzerland.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 16 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 26 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Switzerland. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Difference in salivary DLMO (in minutes, phase advance) between the first and the second night (Shift in dim-light melatonin onset (DLMO)) (time frame: On the evenings of each LE protocol (from 5 hours before habitual bedtime (HBT) (every 30 minutes)) and in the mornings during the first hour after wake-up (8h later) on day 8-10, day 15-17, day 22-24.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 26 Sep 2025.