Grant funding supporting the study ended.

Study investigators want to learn more about the underlying biological clock and to see if the timing of that clock can be estimated from a single blood sample.

There is an urgent need for a practical way to assess circadian timing accurately in both general and sleep medicine. The study is designed to assess the levels of different biomarkers in the blood taken from frequent samples across three separate sleep-wake conditions - Conventional/Normal sleep-wake conditions (baseline), extended wake/acute sleep deprivation (constant routine), and during irregular sleep-wake conditions (inverted day). Participants will be asked to complete medical, psychological, and sleep-wake evaluations prior to the study. Upon completion of screening, if eligible, participants will stay 7 consecutive days and nights in the sleep research laboratory within the hospital.

Inclusion Criteria:

• Healthy adults with conventional and regular sleep-wake timing
• Non-smokers
• Able to spend 7 consecutive days/nights in the laboratory
• Willing to abstain from use of caffeine, nicotine, and alcohol during pre-study and study periods

Exclusion Criteria:

• History of neurological or psychiatric disorder
• History of sleep disorder or regular use of sleep-promoting medication
• Current prescription, herbal, or over-the-counter medication use
• Traveling across 2 or more time zones within the past 3 months
• Donating blood within the past 8 weeks
• Worked night or rotating shiftwork within the past 3 years
• Hearing impairment
• Drug or Alcohol dependency
• Pregnant, intending to become pregnant, or recently pregnant (last 6 months)
• Breastfeeding within the past 6 months

Healthy volunteers will be recruited from the surrounding community.