Effects of Different Colors of Light on Human Physiology

Sponsor

Brigham and Women's Hospital (Other)

Overall Status

Completed

CT.gov ID

NCT00200863

Collaborator

National Center for Complementary and Integrative Health (NCCIH) (NIH)

Enrollment

Location

Arms

Duration (Months)

2.1

Patients Per Site Per Month

Study Details

Study Description

Brief Summary

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.

Condition or Disease	Intervention/Treatment	Phase
Healthy Circadian Rhythm	Device: Monochromatic visible light exposure	N/A

Detailed Description

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.

Study Design

Study Type:

Interventional

Actual Enrollment :

47 participants

Allocation:

Randomized

Intervention Model:

Parallel Assignment

Masking:

None (Open Label)

Primary Purpose:

Treatment

Official Title:

Mechanism Underlying the Effects of Blue Light in Humans

Study Start Date :

Apr 1, 2005

Actual Primary Completion Date :

Feb 1, 2007

Actual Study Completion Date :

Feb 1, 2007

Arms and Interventions

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

Outcome Measures

Primary Outcome Measures

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]

Eligibility Criteria

Criteria

Ages Eligible for Study:

18 Years to 30 Years

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

Yes

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