Evaluation of SmartSleep Technology for Improving the Efficiency and Restorative Quality of Sleep in Healthy Adults

Adequate healthy sleep is essential in spaceflight to ensure that astronauts maintain a high level of cognitive performance capability and do so without undue stress. There is a need for a technology that can improve sleep quality in space and biologically maximize the performance benefits of limited sleep duration, without unduly affecting the ability of astronauts to awaken abruptly and respond to an in-flight emergency. Sleep slow waves support system and synaptic consolidation by promoting specific patterns of neuromodulatory and electric activities, and subjective sleep quality is related to the size and number of slow waves that occur nightly.

This study will use SmartSleep (Philips) technology to determine what effect the device has on daytime cognitive performance after emergent awakenings from sleep in a chronic sleep restriction paradigm. The SmartSleep technology uses two small sensors in the headband to continuously detect the brain's slow wave sleep (delta/theta frequency) in real time, and a closed-loop algorithm customizes the timing and volume of tones to optimize the sleep pattern. Thus, the device uses "quiet audio tones" (sub-awareness) to increase slow waves, which can enhance sleep quality/depth, thereby enhancing subsequent waking cognitive performance without the unwanted sedating effects of medications on cognitive functions during emergency awakenings.

Subjects will be in the laboratory for 7 days/6 nights. Night 1 will be an adaptation night with 8-hours time in bed. Nights 2-5 will consist of 5 hours time in bed, followed by night 6 of a recovery 10 hours time in bed. During nights 2-5, subjects will receive one of four stimulation modalities using the SmartSleep wearable device. Subjects will receive all four modalities in a randomized order:

• Continuous Fixed Interval
• Block
• In-Phase Adjustable
• Sham: No auditory stimulation while wearing the SmartSleep headband

Cognitive performance testing and self-report surveys will be completed on a daily basis. A total of 12 healthy astronaut-like adults will be studied. Subjects will complete the 7-day study in groups of 4.

Inclusion criteria

• Bachelor's degree or Master's degree (or the equivalent in work experience) in a relevant field, and/or military service.
• Free of psychological/psychiatric conditions that preclude participation.
• BMI < 35.
• Self-reported regular sleep schedule; able to maintain their sleep schedule during the course of the study.
• Self-reported sleep duration of 6-8.5 hrs per night (verified by 6 work days of ambulatory sleep monitoring with wrist actigraphy and daily logs).
• Ability to read/write English.

Exclusion criteria

• History of neurological, psychiatric, or other medical condition that excludes participation.
• Current mania or psychosis.
• Current depression as determined by the Beck Depression Inventory (Beck, 1996).
• Alcohol or drug abuse in the past year based upon history and urine toxicology screen.
• Excessive alcohol intake (≥ 21 drinks per week) or binge alcohol consumption (> 5 drinks per day).
• Excessive caffeine consumption (> 650mg/day combining all caffeinated drinks regularly absorbed during the day).
• Current smoker/tobacco user, or using nicotine replacement therapy. Those that have been nicotine-free for 30 days will be included.
• Acute, chronic, or debilitating medical conditions, major Axis I psychiatric illness based on history, physical exam, blood and urine chemistries, and CBC.
• Individuals who self-report a history of recurrent seizures or epilepsy or have a history of medical conditions that could increase the chance of seizures (e.g. stroke, aneurysm, brain surgery, structural brain lesion).
• Cardiovascular, neurological, gastrointestinal, or musculoskeletal problems that exclude participation.
• Major controlled or uncontrolled medical condition such as congestive heart failure, neuromuscular disease, renal failure, cancer, COPD, respiratory failure or insufficiency, or patients requiring oxygen therapy (as determined by self-report).
• Currently working night, swing, split or rotating shift.
• Current use or use of within the past month of a prescription or over-the-counter sleep medication or stimulant; use of psychoactive medication (based on self-report and review with a study clinician).
• Pregnant or currently breast feeding
• Prior history or diagnosis of any sleep disorder
• High Risk of OSA based on STOP-BANG Questionnaire ("yes" on at least 4 of 8 questions)
• High Risk of Restless Legs Syndrome (RLS) based on Cambridge-Hopkins Screening questionnaire
• High Risk of Insomnia based on Insomnia Severity Index (score of 22 or higher)
• Individuals who self-report severe contact dermatitis or allergy to silicone, nickel or silver.
• Individuals who self-report moderate hearing loss.
• Inability to achieve appropriate headband fit.
• Planned travel across more than one time zone one month prior to and/or during the anticipated period of the study with SmartSleeps device use.
• Intentional naps during the week.