Light Exposure for Sleep and Circadian Rhythms

Overseen By Elizabeth B Klerman, MD PhD

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: Massachusetts General Hospital

Must not be taking: Antidepressants, Beta blockers, NSAIDs, others

Disqualifiers: Eye trauma, Neurologic disease, Diabetes, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 1

48 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial investigates how different light exposures affect pupil response, sleep patterns, and hormone levels in healthy individuals. Researchers aim to determine if pupil reactions to light vary based on age and sex and how these reactions relate to sleep and body clock timing. Participants will spend three days in a research setting to undergo non-visual light input tests and monitor their sleep and hormone changes. Individuals who typically fall asleep between 10 p.m. and 1 a.m., wake up between 5:30 a.m. and 8:30 a.m., and have vision correctable to at least 20/30 may be suitable for this study. As an unphased trial, this study offers a unique opportunity to contribute to the scientific understanding of light's impact on health.

Will I have to stop taking my current medications?

The trial requires that participants do not take prescription or non-prescription drugs that affect the pupil, sleep, melatonin, or circadian rhythms. If you are on such medications, you may need to stop taking them to participate.

What prior data suggests that this method is safe for studying sleep and circadian rhythms?

Research shows that light exposure can influence body clocks and sleep patterns. Different types of light, such as blue, green, and red, affect sleep and hormones in various ways. For instance, blue light might impact hormone levels more than red light.

Regarding safety, people generally tolerate these light exposures well. Light is a natural part of the environment, and the study uses it in a controlled manner to better understand its effects. Similar studies have not reported any serious side effects, suggesting this approach is safe for participants. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about this trial because it explores how non-visual light exposure can influence sleep and circadian rhythms by targeting internal body clocks in ways that traditional sleep aids do not. Unlike standard treatments like medication or behavioral therapy, this approach uses specific colors of light—such as red, blue, and green—to test their effects on pupil response, circadian timing, and hormone production. This trial could uncover new, non-invasive ways to improve sleep quality by naturally aligning the body's internal clock, offering a novel alternative to existing therapies.

What evidence suggests that this trial's treatments could be effective for sleep and circadian rhythms?

Research shows that light does more than just aid vision; it also influences the body's internal clock, sleep, and mood. This trial will explore how different types of light exposure affect sleep and circadian rhythms. Studies have found that light therapy can enhance sleep quality and increase total sleep duration. For instance, some light treatments increased melatonin levels, a hormone that helps regulate sleep, by 1.5 times. Other research has discovered that certain types of light exposure can alter the timing of body clocks. This indicates that light can effectively adjust natural sleep/wake cycles, known as circadian rhythms. Participants in this trial will experience different light stimuli to assess their impacts on pupil response, circadian timing, and hormone levels. ^{5 6 7 8 9}

Who Is on the Research Team?

Elizabeth Klerman, MD PhD

Principal Investigator

Massachusetts General Hospital

Are You a Good Fit for This Trial?

This trial is for healthy individuals aged 18-85 with a normal sleep schedule (bedtime between 10 pm and 1 am, wake time between 5:30 am and 8:30 am), vision correctable to at least 20/30, and no major medical issues.

Inclusion Criteria

You usually go to sleep between 10 pm and 1 am.

You usually wake up between 5:30 am and 8:30 am.

Your vision can be improved to at least 20/30 with glasses or contacts.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

1-2 weeks

1 visit (in-person)

Pre-study Monitoring

Participants wear a special watch that monitors their activity and light levels

1 week

In-hospital Testing

Participants live in a research room for 3 days/2 nights for testing pupil response, circadian timing, and hormone responses to light

3 days

Continuous monitoring

Follow-up

Participants are monitored for any delayed responses or effects post-study

2 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Eye Exam
• Melatonin Suppression Test
• Non-visual Light Input
• Pupillometry

Trial Overview

The study examines how pupil response to light varies by age and sex, and its relationship with sleep patterns, circadian rhythms, and hormone responses. Participants will undergo eye exams using pupillometry and be exposed to a light box while staying in a research facility.

How Is the Trial Designed?

Group I: Testing non-visual light impacts on pupil response, circadian timing, and hormones Experimental Treatment 2 Interventions

1. Pupillometry on day 1 in afternoon and evening and on day 2 in morning and evening. Participants will be randomized to one of 8 different light stimuli within the pupillometry 2. Red light exposure on night 1 to determine circadian timing 3. Blue/green light exposure on night 2 to compare hormone response during blue/green light to that during red light on night 1

Who Is Running the Clinical Trial?

Massachusetts General Hospital

Lead Sponsor

Trials

3,066

Recruited

13,430,000+

Published Research Related to This Trial

Light is crucial not only for vision but also for regulating our biological clock, which affects sleep and mood; misalignment between this clock and our sleep schedule can lead to circadian sleep disorders.

Controlled light exposure can be an effective treatment for mood and sleep disorders, with recent studies exploring how different patterns of light and dark can influence our circadian rhythms and overall well-being.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Light exposure in the natural environment: relevance to mood and sleep disorders. Dumont, M., Beaulieu, C.[2007]

Light exposure influences our physiology and behavior through a pathway from the retina to the suprachiasmatic nucleus (SCN) in the hypothalamus, which regulates our circadian rhythms.

There are significant individual differences in how people respond to light's non-visual effects, highlighting the need for more diverse research participants and improved data sharing practices to enhance our understanding of these effects.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Individual differences and diversity in human physiological responses to light. Spitschan, M., Santhi, N.[2023]

Acute exposure to dim light at night (dLAN) slightly disrupted sleep architecture, specifically prolonging the latency to NREM sleep stage N3 and reducing NREM sleep stage 2, but did not significantly affect overall sleep quality or total sleep time.

Despite the changes in sleep architecture, glucose homeostasis remained unaffected by dLAN, suggesting that longer exposure might be necessary to observe any potential metabolic impacts.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Acute mild dim light at night slightly modifies sleep but does not affect glucose homeostasis in healthy men. Chamorro, R., Wilms, B., Holst, A., et al.[2021]

Light can effectively induce sleep in certain rodents through a process called 'photosomnolence,' which involves rapid suppression of movement and a significant drop in body temperature, demonstrating its potential as a nonintrusive sleep stimulus.

The study outlines a straightforward research protocol for inducing sleep with light, allowing for easy assessment of sleep mechanisms without invasive procedures, which could also be relevant for understanding sleep in humans.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A Path to Sleep Is through the Eye Morin, LP.[2018]

In a study of 580 older adults, higher exposure to short-wavelength light at night was linked to poorer sleep quality and increased prevalence of sleep disturbances, with an odds ratio of 1.90 for those in the highest exposure group.

Participants with the highest levels of short-wavelength light exposure also had significantly lower melatonin levels, indicating that this type of light may disrupt normal melatonin production, which is crucial for sleep regulation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Short-wavelength light exposure at night and sleep disturbances accompanied by decreased melatonin secretion in real-life settings: a cross-sectional study of the HEIJO-KYO cohort. Mitsui, K., Saeki, K., Tone, N., et al.[2022]

The study involving 20 healthy participants found that later exposure to light is linked to poorer sleep quality, including more awakenings and shorter time to reach REM sleep, suggesting that light exposure timing significantly affects sleep characteristics.

Higher intensity and earlier light exposure were associated with better sleep architecture, including increased slow-wave sleep, indicating that both the timing and intensity of light can influence sleep regulation and homeostatic sleep pressure.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Linking Light Exposure and Subsequent Sleep: A Field Polysomnography Study in Humans. Wams, EJ., Woelders, T., Marring, I., et al.[2018]

Light therapy is an effective, evidence-based treatment for Seasonal Affective Disorder, influencing circadian rhythms that affect sleep, mood, and cognition, based on 40 years of clinical trials.

For optimal results, light therapy should use devices that provide 10,000 lux of white light for 30-60 minutes in the early morning, with ongoing monitoring to adjust treatment as needed and manage any side effects.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

CME: Light Therapy: Why, What, for Whom, How, and When (And a Postscript about Darkness). Wirz-Justice, A., Terman, AM.[2022]

Dynamic light exposure, which changes spectrum and intensity throughout the day, enhances melatonin secretion and reduces sleep latency compared to static light, suggesting it may improve sleep initiation.

In a study with 14 healthy men, while dynamic light did not significantly affect cognitive performance or sleep quality, it was associated with increased melatonin levels in the evening, indicating potential benefits for sleep regulation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Changing color and intensity of LED lighting across the day impacts on circadian melatonin rhythms and sleep in healthy men. Stefani, O., Freyburger, M., Veitz, S., et al.[2021]

The study emphasizes the importance of standardized reporting guidelines for light exposure in research related to chronobiology and sleep, highlighting seven key aspects that should be measured and reported, such as spectral power distribution and timing properties.

These guidelines aim to improve the consistency and reliability of findings in studies examining the effects of light on non-visual responses in humans, ultimately enhancing our understanding of how light influences sleep and circadian rhythms.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

How to Report Light Exposure in Human Chronobiology and Sleep Research Experiments. Spitschan, M., Stefani, O., Blattner, P., et al.[2021]

A pilot study involving 30 hospitalized patients with major depression showed that dynamic bedroom lighting, which simulates dawn and dusk, improved sleep patterns, leading to earlier wake times and longer sleep durations.

Patients using the dynamic lighting system experienced better sleep efficiency and reduced nighttime awakenings, suggesting that this lighting approach may positively influence the circadian rhythms of individuals starting inpatient treatment for depression.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of dynamic bedroom lighting on measures of sleep and circadian rest-activity rhythm in inpatients with major depressive disorder. Canazei, M., Weninger, J., Pohl, W., et al.[2022]

Light therapy has a moderate positive effect on reducing behavioral disturbances and depression in cognitively impaired individuals, based on a meta-analysis of nine randomized controlled trials.

Higher light intensity (2,500 lux or more) is more effective in alleviating depression compared to lower intensities, and studies with low risk of bias showed better outcomes for behavioral disturbances.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effectiveness of Light Therapy in Cognitively Impaired Persons: A Metaanalysis of Randomized Controlled Trials. Chiu, HL., Chan, PT., Chu, H., et al.[2017]

Light significantly influences the human sleep-wake cycle through its non-image forming effects, which depend on properties like intensity, duration, timing, pattern, and wavelengths.

Understanding how different light characteristics affect sleep can help optimize lighting in homes and workplaces, potentially improving health and aiding in the treatment of sleep-related disorders.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Light Modulation of Human Clocks, Wake, and Sleep. Prayag, AS., Münch, M., Aeschbach, D., et al.[2020]

A pilot study involving 12 hospital employees used a wrist-worn light monitor to track light exposure during a workweek, revealing that the highest light exposure occurred in the 201-500 lux range during work hours.

The findings suggest that prolonged exposure to dim indoor lighting may play a crucial role in regulating circadian rhythms and influencing physiological and behavioral processes in healthy individuals.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Characterizing free-living light exposure using a wrist-worn light monitor. Heil, DP., Mathis, SR.[2019]

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