Investigating the Effects of Evening Light Exposure on Melatonin Suppression, Alertness and Nocturnal Sleep

Not Applicable

Completed

Conditions: Non-visual Photoreception

Interventions: Device: Visible light

Registration Number: NCT01586039

Lead Sponsor: Brigham and Women's Hospital

Brief Summary: The timing and quality of sleep is governed by environmental and physiologic factors. Environmental factors, especially ambient lighting can impact the circadian system and alter the timing and structure of sleep. Light exposure can also acutely alter neural activation state and impair sleep. These effects all demonstrate marked sensitivity to short-wavelength blue light with maximal sensitivity in the 460-480 nm range. The alerting effects of blue light in the evening persist for at least 3-4 hours after the lights are turned off, and can disturb subsequent sleep. Avoiding these deleterious effects of light exposure prior to sleep on subsequent sleep would be beneficial to sleep quality and potentially health.

The investigators will compare the effects of two light sources, equated for visual stimulus (lux), on multiple non-visual responses to light. The investigators will compare a 90 lux exposure of a commercially available Compact Fluorescent Light (CFL) with a novel LED white light source that is depleted in the short-wavelength visible range (Biological Illumination LCC, FL). In a within-subject design, the investigators will test the hypotheses that exposure to a blue-depleted LED as compared to a CFL exposure at (1) 90 lux or (2) 50 lux will cause significantly:

1. Less melatonin suppression between melatonin onset and bedtime;

2. Less subjective and objective alerting responses before bedtime;

3. Less disruption of nocturnal sleep structure and quality.

Detailed Description: Not available

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 33

Inclusion Criteria

(i) Aged between 18-30 years to reduce the confounding effects of lens aging on the transmission of light to the retina;

(ii) Non-smoking for at least 6 months;

(iii) Healthy (no medical, psychiatric or sleep disorders);

(iv) No clinically significant deviations from normal in medical history, vital signs, physical examination, blood chemistry and hematology, urine chemistry and ECG;

(v) Women of childbearing potential must agree to use an acceptable method of birth control, and must have a negative urine pregnancy test;

(vi) Body mass index of > 18 or < 30 kg/m2;

(vii) No drugs or medication likely to affect sleep or alertness, as determined by the investigators;

(viii) Habitual caffeine consumption < 300mg per day on average;

(ix) Habitual alcohol consumption < 10 alcoholic units per week on average.

Exclusion Criteria

(i) History of alcohol or substance abuse;

(ii) Positive result on drugs of abuse screening;

(iii) Current or past history of sleep disorders, including but not limited to obstructive sleep apnea, or any significant sleep complaint;

(iv) Psychiatric disorder;

(v) Recent acute or chronic medical disorder, including but not limited to hepatic impairment and severe chronic obstructive pulmonary disease;

(vi) Visual disorder, including but not limited to color blindness, or family history of glaucoma;

(vii) History of intolerance or hypersensitivity to melatonin or melatonin agonists;

(viii) Pregnancy or lactation;

(ix) Shift work;

(x) Transmeridian travel (2 or more time zones) in past 2 months;

(xi) Any other reason as determined by the Principal Investigator.

Study & Design

Study Type: INTERVENTIONAL

Study Design: FACTORIAL

Arm && Interventions

Group	Intervention	Description
Compact Fluorescent Light 90 lux	Visible light	90 lux exposure of a commercially available Compact Fluorescent Light (CFL).
Blue-depleted LED light 90 lux	Visible light	90 lux exposure of a novel LED white light source that is depleted in the short-wavelength visible range (Biological Illumination LCC, FL).
Compact Fluorescent Light 50 lux	Visible light	50 lux exposure of a commercially available Compact Fluorescent Light (CFL).
Blue-depleted LED light 50 lux	Visible light	50 lux exposure of a novel LED white light source that is depleted in the short-wavelength visible range (Biological Illumination LCC, FL).

Primary Outcome Measures

Name	Time	Method
Melatonin Suppression	6-h constant posture interval of the light exposure	Melatonin suppression is measured as the percentage of melatonin AUC relative to the AUC measured in dim light on the previous day. AUC was calculated during the 6 h of light exposure and the corresponding 6-h interval 24 hours earlier. Higher values indicate more light-induced melatonin suppression.

Secondary Outcome Measures

Name	Time	Method
Subjective Alerting Response	6-h constant posture interval of the light exposure.	Self-reported sleepiness measured during the light exposure using the Karolinska Sleepiness Scale (KSS). Range of scores 1-9, higher score indicate higher subjective sleepiness. Measures were taken hourly throughout the 6-hour constant posture interval of the light exposure and then averaged to calculate a single value per participant.
Sleep Quality	First morning after 8-h time in bed immediately following CFL/LED light exposure.	Self-reported sleep quality was assessed using a post sleep questionnaire. Score on subjective scale range 1-7, higher scores indicate higher sleep quality.
Objective Alerting Response	6-h constant posture interval of the light exposure	Mean reaction time assessed using the 10-minute psychomotor vigilance test. Higher numbers indicate slower reaction times indicating less alertness. Measures were taken hourly throughout the 6-hour constant posture interval of the light exposure and then averaged to calculate a single value per participant.
Sleep Structure	8-h time in bed immediately following CFL/LED light exposure.	Sleep efficiency assessed by polysomnography. Sleep efficiency refers to the percentage of time a person sleeps, in relation to the amount of time a person spends in bed trying to sleep. The percentage is calculated by dividing the Total Sleep Time by the Total Time in Bed.