RecruitingACTRN12621000686808

The Impact of Watch Keeping Schedules on Cognitive Performance and Physiology in Adults

Sponsor

Defence Science and Technology Group - Australian Government Department of Defence

Enrollment

40 participants

Start Date

Jan 15, 2021

Study Type

Interventional

Conditions

Cognitive performance and physiological changes in healthy adults experiencing circadian misalignment

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

Sex: Both males and femalesMin Age: 18 YearssMax Age: 40 Yearss

Plain Language Summary

Simplified for easier understanding

Naval crew members on ships and submarines work in rotating watch schedules that can seriously disrupt sleep and impair cognitive performance — a critical concern when those crew members are responsible for monitoring complex automated systems and responding to emergencies. This study compares two common watch systems: a two-watch (12-hours on, 12-hours off) and a three-watch (8 hours on, 16 hours off) schedule, to find out which leads to better sleep quality, sharper thinking, and healthier physiology. Participants spend time in a controlled laboratory environment simulating the submarine watch schedule, with light exposure manipulated to mimic the absence of natural daylight cycles. Sleep patterns, cognitive tests, and physiological measures are recorded throughout. You may be eligible if you are a healthy adult aged 18 to 40 with normal sleep habits — going to bed after 9 pm on weeknights and waking before 9 am on weekdays. People with cardiovascular disease, neurological conditions, sleep disorders, a BMI over 30, or who use nicotine, heavy alcohol, or illicit drugs are not eligible.

This summary was AI-generated to explain the trial in plain language. It is not medical advice. Always discuss eligibility with your doctor before enrolling in a clinical trial.

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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)

SA, Australia

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ACTRN12621000686808