Studies on the effects of light on human neuroendocrine physiology and cognition
| ISRCTN | ISRCTN88955347 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN88955347 |
- Submission date
- 19/04/2023
- Registration date
- 01/05/2023
- Last edited
- 11/12/2023
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Other
Plain English summary of protocol
Background and study aims
The human brain has a central clock that controls our daily biological rhythms, including our sleep-wake cycle. This central clock receives direct input from light-sensitive cells in the eye, which allows it to stay synchronized with the day and night cycle. The purpose of this study is to examine how our eyes and brain process light to keep our central clock synchronized, and how light exposure in the evening affects our biological rhythms. In particular, this study tries to understand how light information from both eyes is combined in the brain to inform our central clock. The research team have developed an experiment to understand how the effects of light exposure in the evening differ when light is presented in one eye versus presented in both eyes at the same time. The team are also interested in understanding how fast changes in the light in our environment affect this response, so we use flickering lights (turning on and off repeatedly) to examine these mechanisms.
Who can participate?
Healthy people aged between 18 and 40 years old that have normal vision and colour perception
What does the study involve?
The study will last for a total of at least 3 weeks. During this time, volunteers will be asked to avoid travelling across time zones and to maintain a regular bedtime and wake-up time, which will be chosen by them in the initial visit. Throughout the study, they will wear an actigraphy wristwatch that tracks their daily movement and activity, complete a brief sleep diary questionnaire every morning, and log the times of their meals during the day. Participants will be required to abstain from caffeine, nicotine and alcohol for the entire duration of the study. Starting from the second week of the study, participants will visit the laboratory on four evenings, each one at least two days apart. Each visit will last 6 hours, starting 5 hours before their usual bedtime and ending 1 hour after their usual bedtime. During these six hours in the laboratory, they will: Remain seated in dim light for 3 hours, while being allowed to read printed materials or listen to audiobooks or podcasts. After this, they will view a light stimulus using a Virtual Reality headset for two hours (with 10-minute breaks every 20 minutes). During this time, their gaze and pupil size will be recorded. Afterwards, they will return to the dim light for 1 hour. Every 30 minutes, they will provide a saliva sample, do an auditory reaction time test, and complete a brief questionnaire about their sleepiness, perception and mood. Their body temperature will be measured throughout the evening by means of an ingestible temperature capsule. Participants will have access to a toilet and water but will be asked to avoid other drinks or food.
What are the possible benefits and risks of participating?
Participants will have no immediate advantage or benefit from participation in the study, but their data will be used for research purposes with the aim of improving our understanding of the effect of light on daily biological rhythms and the processing of light on the brain. The study is not expected to have any negative impact on the physical health or mental well-being of participants. On the days of visiting the lab, participants will go to bed up to one hour later than usual, which is not associated with any long-term impacts. During the study, volunteers will be subjected to flickering light, which may seem uncomfortable, but is not expected to have any negative effects on their vision or perception. Wearing virtual reality glasses may cause some short-term discomfort after prolonged use, which will be counteracted with frequent breaks.
Where is the study run from?
The Max Planck Institute for Biological Cybernetics, in Tübingen (Germany)
When is the study starting and how long is it expected to run for?
April 2022 to June 2025
Who is funding the study?
Max Planck Society (Germany)
Who is the main contact?
Dr Maydel Fernandez-Alonso, maydel.fernandez.alonso@tuebingen.mpg.de (Germany)
Dr Prof. Manuel Spitschan, manuel.spitschan@tuebingen.mpg.de (Germany)
Contact information
Principal Investigator
Max Planck Institute for Biological Cybernetics
Max-Planck-Ring 8-14
Tübingen
72076
Germany
 ORCID ID |
0000-0002-8572-9268 |
|---|---|
| Phone | +49 7071 601 1670 |
| manuel.spitschan@tuebingen.mpg.de |
Scientific
Max Planck Institute for Biological Cybernetics
Max-Planck-Ring 8-14
Tübingen
72076
Germany
| Phone | None available |
|---|---|
| maydel.fernandez.alonso@tuebingen.mpg.de |
Public
Max Planck Institute for Biological Cybernetics
Max-Planck-Ring 8-14
Tübingen
72076
Germany
| Phone | None available |
|---|---|
| maydel.fernandez.alonso@tuebingen.mpg.de |
Study information
| Study design | Interventional randomized controlled study |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Randomised controlled trial |
| Study setting(s) | Laboratory |
| Study type | Other |
| Participant information sheet | 43525_PIS_v1.02_27March2023.pdf |
| Scientific title | Within-subjects comparison of the effect of evening light exposure of different spatial and temporal properties on melatonin production in healthy adults |
| Study objectives | Spatial (monocular versus binocular) and temporal (constant light versus different temporal frequencies) properties of evening light exposure affect human melatonin production |
| Ethics approval(s) | Approved 19/04/2023, Ethics Committee of Technical University of Munich (Ethikkommission der Technischen Universität München; Ismaninger Straße 22, 81675 München, Germany; +49 (0)89 4140-4199; ethikkommission@mri.tum.de), ref: 2022-439_1-S-SR |
| Health condition(s) or problem(s) studied | Characterisation of non-visual function in healthy participants |
| Intervention | The participants will attend four in-laboratory sessions over a total study period of 3 weeks, including an initial circadian stabilisation period of 1 week. Participants will spend a total of 6 hours in the laboratory during which they will repeatedly give saliva samples for later melatonin assays, complete reaction time and other rating tests. Their pupil size, core body temperature, and other physiological parameters will be monitored throughout each session. In the 2 hours preceding their habitual bedtime, participants will be exposed to one of multiple possible stimuli. The same participant will be exposed to four different stimuli: (A) dim light, (B) constant light, and two active stimulus conditions (C & D). The temporal frequency and spatial properties of the stimulus, and the extent to which stimuli are presented between the two eyes will vary between different participants. Method of randomization All possible sequences of the light stimuli conditions and their combination with the different flicker frequencies possible were added to a list and pseudo-randomized via code in Python. Upon enrollment, each participant is assigned a numerical ID according to the order of enrollment. The experimental code assigns the sequence of the light stimuli and the frequency of flicker that will be delivered via the Virtual Reality headset to each participant, according to their numerical ID. The list containing this information is kept in a file that can only be read via code. The experimenters cannot see the light stimuli during the intervention, and participants are instructed to avoid making comments about the stimuli they see. For each category of intervention provider (e.g. psychologist, nursing assistant), describe their expertise, background and any specific training given. Lead experimenter: Postdoctoral scientist with a background in Psychology and Neuroscience and expertise in human behavioral research. They received training in collecting, processing and storing saliva samples and performing screening tests. Research assistants: Postgraduate and undergraduate students with a background in Psychology and Biology. They received training in collecting, processing and storing saliva samples, as well as in conducting the experiment, giving instructions to participants and assisting with the different screening tests. Modes of delivery: The intervention is delivered in person at the laboratory. The light stimuli are delivered individually for each participant. In each laboratory visit, there might be up to three participants at once. Their privacy is protected via individual booths, where each participant remains throughout the experiment. Describe the type(s) of location(s) where the intervention occurred, including any necessary infrastructure or relevant features The intervention is delivered in the laboratory of the Max Planck Institute for Biological Cybernetics. The space counts with the necessary infrastructure to conduct the experiment. The room where the intervention is delivered has individual booths for each participant. Comfortable seating and an area for personal belongings are provided. Participants have access to a toilet, and all rooms and hallways are kept adequately illuminated. The saliva samples are processed on-site in a separate room that has the centrifuge and freezer for storage. |
| Intervention type | Other |
| Primary outcome measure | Salivary melatonin concentrations measured using a melatonin hormone testing kit at half-hour intervals during a 5-hour evening protocol |
| Secondary outcome measures | The following secondary outcome measures are measured at half-hour intervals during a 5-hour evening protocol: 1. Vigilance measured using the Psychomotor Vigilance Test (PVT) 2. Sleepiness measured using the Karolinska Sleepiness Scale (KSS) 3. Visual comfort measured using a self-report questionnaire |
| Overall study start date | 01/04/2022 |
| Completion date | 30/06/2025 |
Eligibility
| Participant type(s) | Healthy volunteer |
|---|---|
| Age group | Adult |
| Lower age limit | 18 Years |
| Upper age limit | 40 Years |
| Sex | Both |
| Target number of participants | 48 |
| Key inclusion criteria | Current participant inclusion criteria as of 12/07/2023: 1. Age, ≥18, ≤40 years of age, Self-report 2. Physical health, Good physical health, Self-report 3. Mental health, Good mental health, Self-report 4. Ocular health, Good ocular health (self-report) 5. Binocular vision, Titmus Fly Test 6. Visual acuity, Normal or corrected-to-normal visual acuity, Landolt C (20/30 or better) 7. Colour vision, Normal colour vision, Cambridge Colour Test, anomaloscope Previous participant inclusion criteria: 1. Age, ≥18, ≤40 years of age, Self-report 2. Physical health, Good physical health, Self-report 3. Mental health, Good mental health, Self-report 4. Ocular health, Good ocular health, Ophthalmological examination by ophthalmologist 5. Binocular vision, , Titmus Fly Test 6. Visual acuity, Normal or corrected-to-normal visual acuity, Landolt C 7. Colour vision, Normal colour vision, Cambridge Colour Test, anomaloscope |
| Key exclusion criteria | Current participant inclusion criteria as of 12/07/2023: 1. BMI, <18 or >30, Calculation from self-reported and/or measured height and weight 2. Medication use, Any use of medications, Self-report 3. Smoking, Habitual smoking, Self-report 4. Epilepsy, Diagnosis of epilepsy in self or close relatives with epilepsy (parents, siblings, children), Self-report 5. Substance abuse, Excessive alcohol use, AUDIT > 7 6. Sleep, Poor sleep quality, PSQI >5 7. Chronotype, Extreme chronotype, MCTQ 8. Shift work, No shift work in the past 3 months, Self-report 9. Time zone travel, No inter-time zone travel with more than 1-hour difference in the past 3 months, Self-report 10. Excessive daytime sleepiness, ESS > 12 11. Exogenous hormone intake, including hormonal contraceptives, Self-report 12. Pregnant or breastfeeding, Self-report 13. Hormonal disorders, Self-report 14. Frequent severe physical symptoms related to the menstrual cycle (headache, fever, nausea, vomiting, severe pain), Self-report Previous participant inclusion criteria: 1. BMI, <18 or >30, Calculation from measured height and weight 2. Medication use, Any use of medications, Self-report 3. Smoking, Habitual smoking, Self-report 4. Epilepsy, Diagnosis of epilepsy, Self-report 5. Substance abuse, Excessive alcohol use, AUDIT 6. Sleep, Poor sleep quality, PSQI >5 7. Chronotype, Extreme chronotype, MEQ 9. Shift work, No shift work in the past 3 months, Self-report 10. Time zone travel, No inter-time zone travel in the past 3 months, Self-report |
| Date of first enrolment | 19/04/2023 |
| Date of final enrolment | 31/12/2024 |
Locations
Countries of recruitment
- Germany
Study participating centre
Tübingen
72076
Germany
Sponsor information
Research organisation
Max-Planck-Ring 8-14
Tübingen
72076
Germany
| Phone | +49 (0)7071 601-500 |
|---|---|
| presse-kyb@tuebingen.mpg.de | |
| Website | http://www.kyb.tuebingen.mpg.de/ |
"ROR" |
https://ror.org/026nmvv73 |
Funders
Funder type
Research organisation
Government organisation / Research institutes and centers
- Alternative name(s)
- Max Planck Society for the Advancement of Science, Max-Planck-Gesellschaft zur Förderung der Wissenschaften, Max Planck Society, MPG
- Location
- Germany
Results and Publications
| Intention to publish date | 31/12/2025 |
|---|---|
| Individual participant data (IPD) Intention to share | Yes |
| IPD sharing plan summary | Stored in publicly available repository |
| Publication and dissemination plan | 1. Planned publication in a high-impact peer-reviewed journal 2. Presentation at relevant scientific conferences and workshops |
| IPD sharing plan | The datasets generated during and/or analysed during the current study will be stored in a publicly available repository (FigShare and GitHub). Raw, individual-level data with appropriate metadata will be made available via FigShare.org at the time of submission of the peer-reviewed article or preprint. No restrictions are placed on the data. Data will be fully anonymised, and participants are informed of this in the Informed Consent form. |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Participant information sheet | version 1.02 | 27/03/2023 | 01/05/2023 | No | Yes |
| Participant information sheet | version 1.02 | 27/03/2023 | 01/05/2023 | No | Yes |
Additional files
Editorial Notes
11/12/2023: The following changes were made to the trial record:
1. The recruitment end date was changed from 31/12/2023 to 31/12/2024.
2. The overall end date was changed from 31/12/2024 to 30/06/2025.
3. The intention to publish date was changed from 31/12/2024 to 31/12/2025.
4. The plain English summary was updated to reflect these changes.
12/07/2023: The following changes have been made:
1. The participant inclusion criteria were changed.
2. The participant exclusion criteria were changed.
01/05/2023: Trial's existence confirmed by the Ethics Committee of Technical University of Munich (Germany).
