Sleep more or less? study reveals gut bacteria shifts in night owls

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Men between 20 - 50 years of age and pre-menopausal women between 20 - 45 years of age (inclusive). 2. Consistent schedule during daytime hours. 3. BMI 18.5 - 35 kg/m2 (inclusive). 4. Good physical and mental health as established by self-reported medical history. 5. Willingness to maintain and record their general habits, eating, and activity/exercise pattern for the study period. 6. Willingness to maintain and record the same time in bed they have during the workdays throughout the habitual workday sleep period. 7. Able to alter sleeping time during the study intervention period as instructed. 8. Willingness to maintain typical sleep hygiene patterns (e.g. sleep location, temperature, environment). 9. Willingness to maintain their current pattern of alcohol consumption for the duration of the study. 10. Willing and able to participate fully in all aspects of the study and complete all study procedures, including providing signed informed consent. 11. Completes all study procedures during the 14-day screening period to be eligible for the cohort specific criteria based on the sleep data collected during the screening period. 12. Has regular bowel habits with bowel movements on at least 5 days a week. 13. Pittsburgh Sleep Quality Index (PSQI) score ≤10. Note: If PSQI score is between 8 and 10, PI discretion needed to confirm eligibility based on self-report screening diaries and health \& lifestyle questionnaire. Cohort specific inclusion criteria: Cohort 1 (Insufficient Sleep) Participants must meet all general inclusion criteria PLUS: 1. Sleep, on average, 5-7 hours per night on workdays, verified via participant self report during the screening period. Note: Oura ring data from the run-in period will be reviewed to confirm cohort based on PI/Sponsor discretion. 2. Average KSS Score of 6-10 on workdays during the screening period. Note: Use standard rounding rules for averages with decimal places. Cohort 2 (Sufficient Sleep) Participants must meet all general inclusion criteria PLUS: 1. Sleep, on average, 7-9 hours per night on workdays, verified via participant self-report during the screening period. Note: Oura ring data from the run-in period will be reviewed to confirm cohort based on PI/Sponsor discretion. 2. Average KSS Score of 1-5 on workdays during screening period. Note: Use standard rounding rules for averages with decimal places. Exclusion: 1. Any current diagnosed or self-reported sleep disorder, including but not limited to sleep apnea, habitual snoring (defined as loud, persistent snoring 3 or more nights per week), insomnia, narcolepsy, and parasomnias. 2. Any current diagnosed or self-reported gastrointestinal disorder, including Crohn's disease, ulcerative colitis, celiac disease, IBS, or functional bowel disorder or chronic heart burn. 3. Regularly wakes up during the night 5 or more times per night for a cumulative amount of 30 minutes as observed via self-report during the screening period, per Principal Investigator (PI) discretion. 4. Currently taking medications (including over-the-counter medications) or dietary supplements that, in the investigator's opinion, may affect the participants' microbiome or sleep. 5. Have taken in the last 3 months medications (including over-the-counter medications) or dietary supplements that, in the investigator's opinion, may affect the participants' microbiome or sleep. 6. Neurodegenerative diseases (including multiple sclerosis, Parkinson's disease, Alzheimer's disease, dementia). 7. Recent history (current use or within the past 1 month) of smoking, vaping or other use of nicotine-containing products. 8. Recent history (past year) of alcohol abuse or dependence. Defined as regularly drinking more than 12 drinks for females and more than 20 drinks for males per week and based on PI discretion. 9. Drug abuse or dependence, including consistent recreational substance use such as marijuana. 10. Binge drinking behavior, defined as 4 or more alcoholic drinks for women or 5 or more alcoholic drinks for men in one sitting on 2 or more occasions, within the past 1 month with final decision per PI discretion. 11. Diagnosed neuropsychiatric disorders or symptoms possibly affecting sleep (generalized anxiety disorder (GAD), major depressive disorder (MDD), bipolar disorder, schizophrenia) 12. Any use of systemic antibiotics in the past 3 months. Topical or targeted antibiotic use (eye drop, ear drop) are allowed. 13. Any use of probiotic supplements in the past 2 weeks. 14. Any use of proton pump inhibitors (PPIs) in the past 2 weeks. 15. Pregnant or breastfeeding or planning to become pregnant. 16. Personal life situation causing stress or challenges in sleep (eg. caretaker required to wake up during sleep, major change in personal life). Note: Life situations causing stress or challenges in sleep that are considered short-term, per PI discretion, may be considered for re-screening 4 weeks after the life situation has resolved, meaning it is no longer causing stress or challenges in sleep. 17. Planned overnight or cross time zone travel during the study. 18. Females experiencing perimenopausal or menopausal symptoms, or those who have been diagnosed as perimenopausal or menopausal by a physician. 19. Any diagnosed condition or undiagnosed symptom which disrupts sleep, including, but not limited to, hyperthyroidism, night sweats, restless legs, or poorly controlled allergic rhinitis. 20. Extreme chronotypes for Cohort 2 (Sufficient Sleep); those that regularly go to sleep prior to 08:00 pm or after 2:30 am on 3 or more nights a week. 21. Extreme chronotypes for Cohort 1 (Insufficient Sleep); those that regularly go to sleep prior to 08:00 pm on 3 or more nights a week. 22. Varying work schedule and/or shift workers who work overnight shifts (e.g. 3rd shift, working late night to early morning hours) 23. Any other personal or medical condition that the investigator believes may bias or confound the results.