Caffeine Optimization Versus Standard Caffeine Dosage (2B-2)

Inclusion criteria

• Age 18-39 years of age
• Must demonstrate adequate comprehension of the protocol by achieving a score of at least 80% correct on a short multiple-choice quiz

Exclusion criteria

• Self-reported habitual nightly sleep amounts outside the target range of approximately 6-9 hours (i.e., less than 6 hours per night or more than 9 hours per night, on average)
• Self-reported nighttime bedtimes earlier than approximately 2100 hours on average during weeknights (Sunday through Thursday)
• Self-reported morning wake-up times later than approximately 0900 on average during weekdays (Monday through Friday)
• Self-reported habitual napping (\> 3 times per week)
• Self-reported symptoms suggestive of a sleep disorder (to include but not limited to sleep disordered breathing/sleep apnea, narcolepsy, idiopathic hypersomnia, restless leg syndrome, parasomnias, rapid eye movement (REM) behavior disorder, etc.)
• History of a sleep disorder (to include all of the above)
• Any use of prescription or over-the-counter sleep aids during the 6-month period prior to screening indicative of a potential sleep disorder as determined by the examining study physician
• History of neurologic disorder (e.g., seizure disorder, amnesia for any reason, hydrocephalus, multiple sclerosis)
• Self-reported caffeine use \> 400 mg per day on average
• Score of 14 or above on the Beck Depression Inventory (BDI)
• Score of 41 or above on the Spielberger Trait Anxiety Inventory (STAI-T)
• Score below 31 or above 69 on the Morningness-Eveningness Questionnaire
• Self-reported regular nicotine use (\> 1 cigarette or equivalent per week) within the last 1 year) or positive nicotine/cotinine result during screening visit
• Self-reported heavy alcohol use (≥14 drinks per week or as determined by the examining study physician) or positive saliva alcohol result during screening visit
• History of cardiovascular disease (to include but not limited to arrhythmias, valvular heart disease, congestive heart failure, history of sudden cardiac death or myocardial infarction)
• Underlying acute or chronic pulmonary disease requiring daily inhaler use
• Kidney disease or kidney abnormalities
• Liver disease or liver abnormalities
• Self-reported history of psychiatric disorder requiring hospitalization or use of psychiatric medication for any length of time
• Self-reported use of products or drugs that cannot be safely discontinued during in-laboratory phases (determined on a case-by-case basis by the examining study physician)
• Self-reported current use of other illicit drugs (to include but not limited to benzodiazepines, amphetamines, cocaine, marijuana) or positive urine drug screen
• (Females only) positive urine pregnancy result
• (Females only) self-reported or suspected current breast-feeding or collecting breast milk
• Resting blood pressure above 140/90 or resting pulse \> 110 beats per minute (if a physician performs a repeat measurement, \~20 minutes after original measure, and it is within range, volunteer will not be excluded)
• BMI ≥ 30 (Obese Class I or greater)
• Clinically significant values (as determined by the reviewing study physician) for any hematology or chemistry parameter
• Inability to read and sign consent
• (Military only) failure to obtain required approved official leave to participate
• Failure to cooperate with requirements of the study, e.g. failure to complete 80% of Smart-Psychomotor Vigilance Tests (PVTs) during Phase 1 (Days 2-13)