Sleep Length and Circadian Regulation in Humans

Study Overview
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Brief Summary
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This research will examine why sleep restriction reduces the body clock's response to bright light. The results will enable the optimization of the bright light treatment of people who suffer from circadian rhythm sleep disorders, which include shift work sleep disorder, jet lag, delayed sleep phase syndrome and winter depression, thereby improving public health and safety, well-being, mood, mental function, and quality of life.

Detailed Description
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Millions of Americans suffer from circadian rhythm sleep disorders, which include shift work sleep disorder, jet lag, delayed sleep phase syndrome and possibly winter depression. These conditions are typically characterized by persistent insomnia and/or excessive daytime sleepiness, impaired performance, and gastrointestinal distress. These negative symptoms result from a misalignment between the timing of the external social world and the timing of the internal circadian (body) clock. Circadian rhythm sleep disorders are effectively treated with bright light, which phase shifts the circadian clock, thereby realigning it with the timing of the external social world. It is widely recognized that social influences have led to an increasing prevalence of sleep restriction in modern society. We recently demonstrated for the first time that short sleep episodes, when compared to long sleep episodes, markedly reduce phase advances to bright light. Thus when people cut their sleep short, they inadvertently reduce their circadian responsiveness to bright light. The mechanism(s) behind these reduced phase shifts to light are unknown. However, there are at least two aspects of short sleep episodes that could be responsible for this effect. First, short sleep episodes are associated with partial sleep deprivation. Second, as humans sleep with their eyes closed and are usually exposed to light when awake, short sleep episodes are also associated with short dark lengths. Our overall goal is to determine the biobehavioral mechanisms by which short sleep episodes impair phase shifts to bright light. Specific Aim 1 is to determine the effect of partial sleep deprivation on phase advances to light, while controlling for dark length. Specific Aim 2 is to determine the effect of short dark lengths on phase advances to light while minimizing sleep deprivation. We will estimate the timing of the human circadian clock by measuring salivary melatonin, a neuroendocrine hormone released from the pineal gland, and collecting measures of sleep via actigraphy, and sleepiness, mood, gastrointestinal distress and cognitive performance via computerized assessment. Characterization of the separate effects of sleep deprivation and dark length on circadian phase shifts to light in humans is critical to understanding how humans respond to light during their daily life activities. Furthermore, the findings of this research will produce important and practical recommendations for avoiding decrements to phase shifts to light, thereby optimizing the bright light treatment of circadian rhythm sleep disorders, and thus improving public health and safety, well-being, mood, cognitive function, and quality of life.

Official Title
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Sleep Length and Circadian Regulation in Humans

Conditions
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Sleep Disorders

Intervention / Treatment
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* Device: Bright light box


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy adult volunteers Exclusion Criteria: color blindness with the Ishihara test obese people (BMI > 30)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 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: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: 9 hour sleep, then 3 hour nap and 6 hour sleep<br> | Device: Bright light box<br>* Bright light of about 5000 lux, administered while sitting at a desk.<br>|
| Active Comparator: 3 hour nap and 6 hour sleep, then 9 hour sleep<br> | Device: Bright light box<br>* Bright light of about 5000 lux, administered while sitting at a desk.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Dim Light Melatonin Onset (Hours) | Gold standard marker of circadian timing | 12 days from baseline to final dim light melatonin onset | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Psychomotor Vigilance | Fastest 10% reaction time (msec) | after short or long nights | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Circadian Rhythms