Effects of Different Colors of Light on Human Physiology

Study Overview
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Brief Summary
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This study will determine which color of light is most effective in stimulating a range of biological functions in humans including activation of sleep-wake regulatory system (alertness, performance, microsleeps, brain activity), activation of the nervous system (heart rate, temperature, blood pressure, breathing rate), and shifting the timing of the internal 24-hour (circadian) pacemaker.

Detailed Description
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Light has long been proposed to have a stimulatory effect on a range of biological functions in humans including increased feelings of activation, such as improved alertness or ability to perform. The mechanisms underlying how light stimulates these neurobiological systems remain to be elucidated. We propose to investigate the effects of different colors of light on human physiology, and in particular, test the claims that specific colors of light preferentially stimulate neurobiological, physiological and hormonal systems. Using classical photobiological techniques, we will construct action spectra for the effects of different colors of light on a range of non-image forming responses in humans. We will test the hypotheses that: 1) light-induced activation of the neurobiological sleep-wake regulatory system, as indicated by increased alertness, faster reaction time, suppression of EEG alpha activity, microsleeps and slow rolling eye movements, and suppression of pineal melatonin, is most sensitive to retinal exposure to short wavelength blue light (460 nm) compared to equal photons of other colors of visible light; 2) light-induced activation of autonomic and hypothalamic-pituitary-adrenal axis measures of arousal, as indicated by increased heart rate variability, core body temperature, blood pressure, respiration rate, plasma cortisol levels and urinary catecholamines, is most sensitive to exposure to short wavelength blue light (460 nm) compared to equal photons of other colors; 3) phase shifts of the human circadian pacemaker, as assessed by changes in temperature, melatonin and cortisol rhythms, are most sensitive to exposure to short wavelength blue light (460 nm) compared to equal photons of other colors. The resultant action spectra will help to identify the photoreceptor mechanism(s) by which light activates arousal and circadian resetting, these non-image-forming physiological responses and enable us to distinguish between major candidate photoreceptive mechanisms, including potential novel photoreceptor systems, that might mediate such responses.

Official Title
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Mechanism Underlying the Effects of Blue Light in Humans

Conditions
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Healthy, Circadian Rhythm

Intervention / Treatment
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* Device: Monochromatic visible light exposure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Free from any acute, chronic or debilitating medical, psychological, or ophthalmological conditions Drug-free (including caffeine, nicotine, and alcohol) for entire study duration Exclusion Criteria: History of drug or alcohol dependency History of psychiatric illnesses or evidence of psychopathology according to standardized questionnaires, or in a structured clinical interview Night shift work during the past 3 years Transmeridian travel in the last 3 months

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 1<br>420 nm light | Device: Monochromatic visible light exposure<br>* Monochromatic light in the visible range from 420-620 nm up to 60uW/cm2 for 6.5 hours<br>|
| Experimental: 2<br>480 nm | Device: Monochromatic visible light exposure<br>* Monochromatic light in the visible range from 420-620 nm up to 60uW/cm2 for 6.5 hours<br>|
| Experimental: 3<br>507 nm | Device: Monochromatic visible light exposure<br>* Monochromatic light in the visible range from 420-620 nm up to 60uW/cm2 for 6.5 hours<br>|
| Experimental: 4<br>555 nm | Device: Monochromatic visible light exposure<br>* Monochromatic light in the visible range from 420-620 nm up to 60uW/cm2 for 6.5 hours<br>|
| Experimental: 5<br>620 nm | Device: Monochromatic visible light exposure<br>* Monochromatic light in the visible range from 420-620 nm up to 60uW/cm2 for 6.5 hours<br>|
| Experimental: 6<br>460 nm | Device: Monochromatic visible light exposure<br>* Monochromatic light in the visible range from 420-620 nm up to 60uW/cm2 for 6.5 hours<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Subjective alertness prior to, during and after light exposure |  | 9.5 hours | 
| Auditory psychomotor performance prior to, during and after light exposure |  | 9.5 hours | 
| EEG power frequency prior to, during and after light exposure |  | 9.5 hours | 
| Plasma melatonin and cortisol prior to, during and after light exposure |  | 60 hours | 
| Heart rate, blood pressure, respiration rate and temperature prior to, during and after light exposure |  | 9.5 hours | 
| Urinary catecholamines prior to, during and after light exposure |  | 32 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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arousal, light, wavelength, action spectrum, circadian, melatonin, alertness, performance