Can Ammonium Inhalants Maintain Performance in Sleep Deprived Soldiers?

This study aims to examine the effectiveness of ammonia inhalants in countering the effects of total sleep deprivation on cognitive and physical performance tests relevant to military personnel.

Data from this study are part of a broader research project aimed at investigating the effects of different light conditions on cognitive and physiological performance during periods of total sleep deprivation. We used a crossover randomized controlled trial design with within-subject repeated-measures to assess the effects of \~36 hours of total sleep deprivation and acute ammonia inhalation on occupationally relevant military tasks in military personnel.

Participants reported to the Sleep and Chronobiology laboratory (National Institute of Mental Health) on Thursday evening after a standardized dinner at \~1800 h. They then completed a series of questionnaires addressing psychological and physiological health, which were followed by a general familiarization of the layout of the facility (i.e., location of the bathrooms, testing stations, etc.). During this familiarization, the participants were also familiarized with the specific testing procedures and practiced each of the required tasks.

The actual testing protocol began with a night of uninterrupted sleep from \~2200 h to \~0630 h. Participants then underwent 5 identical testing sessions from every \~0730-0930 h in the morning and \~1900-2100 h in the evening. The first test occurred in the morning after the full night of baseline sleep (0 h) and again after 12 hours (-12 h), 24 hours (-24 h), and 36 hours of total sleep deprivation (-36 h) followed by additional testing session after 8 hours (from 2230-0630 h) of recovery sleep (+8 h). During total sleep deprivation, participants were not allowed to sleep and were kept awake in a common room by passive means, such as playing board games, watching television and reading books while under constant supervision of the research team. Furthermore, the participants were subjected to a constant ambient room light for the entire duration of total sleep deprivation period.

Participants were administered a standardized sleepiness scale and underwent simple reaction time testing, handgun shooting accuracy protocol, a rifle disassembly and reassembly protocol, and countermovement jump testing at each testing session. Participants performed each individual test twice at each testing period, either with AI (AI) or without AI (CON), in randomized order and separated by 2 minutes of rest (in order to minimize any potential carryover effects of the AI)

For all AI trials, a capsule containing 0.3 mL of AI (composed of 15% of ammonia and 35% of alcohol) (31) was used according to the manufacturer's instructions (Dynarex Corporation, Orangeburg, NY). When the ammonia fumes were released, researcher immediately held the capsule under the participant's nose to inhale until a voluntary withdrawal reflex was observed.

During the entire study protocol, participants received personalized daily food rations consisting of standard 'ready to eat' meals commonly used in the Czech military. One week before the experiment, participants' body composition was measured (using air displacement plethysmography; Bod Pod Body Composition System; Life Measurement Instruments, Concord, CA), and the total daily energy expenditure was derived from the estimated resting metabolic rate and application of an "active" physical activity factor of 1.6 to the individual caloric requirements. In addition, each participant was allowed ad libitum water consumption. Breakfast was consumed at \~0930 h, lunch at \~1230 h, and dinner at \~1730 h, each day. Additionally, all forms of stimulants were prohibited 72 hours before and during the testing protocol.

Eligibility Criteria:
Inclusion Criteria:

* passed an annual physical fitness test
* passed medical checkup within the last year
* have at least two years of active-duty service experience
* report a high level of comfort handling firearms
* non-smokers
* currently not working shift-work
* not taking medications known to interfere with sleep, cognitive or physical performance.

Exclusion Criteria:

* smoker
* did not pass an annual physical fitness test
* did not pass medical checkup within the last year
* work in Shift-work