The Impact of Watch Keeping Schedules on Cognitive Performance and Physiology in Adults
Defence Science and Technology Group - Australian Government Department of Defence
40 participants
Jan 15, 2021
Interventional
Conditions
Summary
Modern navies are focused on trying to shrink the size of their crews to exploit the benefits of new achievements in automation of ships systems. While technological advances are enablers, the performance of these advanced systems is only as good as the crews who man them. The ability to remain vigilant for an automation failure is impacted more severely by fatigue than are other mental functions. From a fatigue management point of view, most navies have sub-optimal watch systems that unnecessarily fatigue naval crews which results in sub-optimal crew performance. An overlooked opportunity exists on Subsurface vessels in that the natural light dark cycles can be manipulated. Theoretically this would be advantageous for a 2 watch system, but this is never been attempted under laboratory conditions. We hypothesise that sleep, cognitive performance, and physiological measures will differ between the watches within both a two-watch routine, and a three-watch routine. The research question is whether a two-watch or three-watch routine lead to better sleep, cognitive performance, and physiological functioning.
Eligibility
Inclusion Criteria1
- Healthy, young adults (18-40 years) with normal sleep/wake behaviour (self reported).
Exclusion Criteria3
- Self reported habitual nightly sleep amounts < 6 or > 9 hours; self reported night time lights out earlier than 2100 hours during weeknights; self reported morning wake-up times
- later than 0900 during weekdays; self reported habitual napping > 1 time a week; self reported caffeine use > 400 mg (e.g. 8 caffeinated sodas or approximately 3 to 4 cups of coffee) per day, history of cardiovascular disease (including but not limited to arrhythmias, valvular heart disease, congestive heart failure, or myocardial infarction); history of neurologic disorder (including but not limited to epilepsy or another seizure disorder,
- amnesia for any reason, hydrocephalus, MS, narcolepsy or other sleep disorder); underlying pulmonary disease requiring daily inhaler use; kidney disease or abnormalities, liver disease or abnormalities; self reported history of psychiatric disorder requiring hospitalization or psychiatric product for any length of time; self reported or suspected regular nicotine use (> 1 cigarette or equivalent per week) within the last year; self reported or suspected heavy alcohol use (minimum limit to define heavy alcohol use is 14 drinks per week or as determined by the examining study licensed physician); self reported or suspected current use of other illicit drugs (including but not limited to benzodiazepines, amphetamines, cocaine, marijuana); resting blood pressure above 140/90 or resting pulse > 110; BMI > 30 (Obese Class I or greater); clinically significant values (as determined by the reviewing study physician) for any haematology or chemistry parameter; positive urine drug result during screening visit; currently taking corticosteroid or anti-inflammatory medications.
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Interventions
Trained research assistants will deliver ten x 9 night lab study runs, monitoring participant adherence to the protocol at all times during the 10 day in-laboratory visit which will be overseen by the chief investigators of the study. will be conducted, with 16 participants undergoing a two-watch routine (2 conditions, 12h on and 12 off watch) 12) and 16 participants undergoing a three section watch routine (2 conditions, 8h on 16h off watch). On training day (day 1) participants will be talked through each neurobehavioral task and be given time to ask questions and familiarise themselves with the laboratory, followed by an 8h acclamation sleep. Participants will be given 6.5 hour sleep opportunities in each condition. The conditions differ in the timing of this sleep opportunity; A) 0930 to 1600, B) 0830 to 1230 and 2130 to 0000 C) 1800 to 0030, D) 0130 to 0800. On the 9th night participants will be given a 8h recovery sleep from 2300 to 0700. Neurobehavioural and physiological functioning will be measured in blocks simulating shifts; A) 0000 to 0900 and 1700 to 2100, B) 0000 to 0700 and 1300 to 1900, C) 0000 to 0500 and 1300 to 1700. D) 0900 to 1300 and 2100 to 0100. Variables that will be measured from the laboratory will be: a) Cognitive performance: Psychomotor Vigilance task (reaction time and errors), cognitive throughput (number correct), working memory (correct answers), vigilant attention (maintenance of performance), decision making (correct responses), inhibition (correct responses), CRUSE Submarine simulator (situation awareness) b) Team work task (COHESION task) c) Physiological state: heart rate, heart rate variability d) Eye tracking (desk mounted eye tracking device used during simulated drive) e) Salivary and blood cortisol and melatonin f) Sleep monitoring: sleep onset latency, sleep quality, percent time in each sleep stage, total sleep time, arousals g) Subjective ratings of fatigue, sleepiness, performance, and questionnaires on mood, physiological symptoms. Saliva samples will be taken at 2h intervals on each day of the protocol. Blood samples will be taken once at baseline and once following recovery sleep. All sleeps will be recorded by standard polysomnography. As part of this recording, electrodes will be attached to participants' scalps, the skin on their face, chin and chest during the scheduled sleep, to measure their brain activity and heart rate during sleep. All sleeps will be recorded by standard polysomnography. As part of this recording, electrodes will be attached to participants' scalps, the skin on their face, chin and chest during the scheduled sleep, to measure their brain activity and heart rate during sleep.
Locations(1)
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ACTRN12621000686808