The Microbiome and Responsiveness to Stress: Countermeasure Strategies for Improving Resilience to Sleep and Circadian Disruption (Experiments 1 & 2)

Experiment 1: Consistency of microbiota-gut-brain axis responses

Prior to the start of this study, there are screening procedures to ensure participants meet the criteria for the study. At the first consent screening appointment, participants will learn more about the study, answer questionnaires, and complete a psychological interview. At the second medical screening appointment, participants will have a physical exam, blood work, drug screen, pregnancy test, electrocardiogram (a measurement of heart activity), and a resting metabolic rate assessment (a measurement of how much energy the body uses at rest). Participants will also meet with a nutritionist to discuss their food preferences for the study. Although participants are not financially compensated for the screening procedures, the expense of the screening tests is covered and copies are provided to the participant upon request. All of the results of the screening procedures are confidential and will only be used by the study staff to determine eligibility for the study.

Following the screening procedures, participants will complete two laboratory visits, both visits preceded by two weeks of home activity monitoring. During the home monitoring, participants wear a special watch that records activity levels. Participants also keep a sleep/wake log and use a website to log their daily sleep/wake times (if participants cannot access this website, they can call into an answering machine to inform investigators when they go to bed and wake up each day). The investigators will provide participants with a pre-study diet prepared by study dieticians for participants to eat for the three days prior to the laboratory visit. During the two weeks between the first and second laboratory visit participants will continue to wear the special watch, keep a sleep/wake log, and use a website to log their daily sleep/wake times (or call them into the answering machine). Participants will again be given a pre-study diet for the three days prior to their second visit.

During the laboratory visits, participants will live in the Sleep and Chronobiology Lab at the University of Colorado at Boulder for 3.7 days on two different occasions. The day before the inpatient visit begins, participants will spend the night in the laboratory, sleeping their normal 8 hours. This will be used as a pre-study screening for problems with sleep. In the morning participants will complete some pre-study tests and samples which will take approximately 60 minutes. Participants will then be permitted to leave the laboratory and in the evening they will return to begin the study. During the study participants sleep schedule will be changed to simulate the sleep loss that emergency workers in medical and military situations experience. Participants will be given an initial 3 hour sleep opportunity and then kept awake overnight. Throughout the study participants will be given a 3 hour sleep opportunity for every 24 hours of the laboratory visit. While participants are awake, they will be asked to perform a number of computer tasks, including a driving simulator. Blood and saliva samples will be taken to test for circadian and metabolic markers. Participants will also be asked to collect samples of the bacteria that live in their gastrointestinal tract from used bathroom tissue after they use the bathroom in the study. Finally, investigators will test how the heart and nervous system respond to stress by having participants place their hand in an ice water bath. At the end of the laboratory visit participants will be given an 11 hour sleep opportunity to recover from their sleep loss. After 3 more days of recovery sleep and another 2 weeks of home monitoring (identical to the first two weeks of the study), these procedures will be repeated in a second laboratory visit.

Experiment 2: Pre-biotic