Gap Sleep3: Does sleep loss continue on long duration spaceflight or is there adaptation? What is the nature of circadian desynchronization, extended wakefulness and work overload over long duration missions? (Closed)
Last Published:  07/31/19 10:05:30 AM (Central)
Responsible Element: Behavioral Health and Performance (BHP)
Status: Closed
Closure Rationale

The NASA Human Research Program (HRP) Behavioral Health and Performance Element (BHP) manages a research portfolio related to characterizing and mitigating three human health risks, including the Risk of Performance Errors due to Fatigue Resulting from Sleep Loss, Circadian Desynchronization, Extended Wakefulness and Work Overload (“Sleep”). One of the identified research gaps for this risk, gap Sleep 3, reads: “Does sleep loss continue on long duration spaceflight or is there adaptation? What is the nature of circadian desynchronization, extended wakefulness and work overload over long duration missions?”

 

This knowledge gap as addresses the need to characterize the nature of sleep, circadian desynchronization, extended wakefulness and work overload, over the course of a long duration mission in space. Anecdotal reports indicate that on the ISS (as well as in other spaceflight missions), many crew members often do not sleep for the duration of their scheduled sleep period, and that circadian desynchronization, extended wakefulness and work overload are also regularly experienced by the crew [1]. In attempt to systematically collect objective data to further characterize this risk, BHP sponsored a NASA investigation, Sleep-Wake Actigraphy and Light Exposure During Spaceflight (“Sleep-Wake”). 

 

The Sleep-Wake protocol included 60 astronauts across 80 shuttle missions and 21 astronauts on ISS missions. Participants wore a small light-weight ambulatory recording device (Actiwatch-L) which provided an assessment of sleep-wakefulness activity via wrist actigraphy and light-exposure levels. A sleep log that allowed crewmembers to record their subjective assessment of their sleep, as well as specific countermeasures used, was also maintained – daily for shuttle flyers, and every three weeks for ISS crewmembers.

 

A report of the findings is awaiting publication, but in the interim the principal investigators – Drs. Laura Barger and Charles Czeisler – have provided a preliminary report for limited internal distribution [2]. Relevant findings from this report reveal that:

 

  • Sleep, on average, is reduced on ISS, as during Shuttle missions. Sleep deficiency on ISS missions was similar to the approximately six hours of sleep experienced on short duration Shuttle missions (p=0.31). Astronauts slept significantly less on ISS missions compared to L-90 pre-flight and post-flight. The similar pre-flight to in-flight durations are largely attributed to the intense training schedule.
  • On 44% of nights aboard ISS missions, astronauts obtained less than 6 hours of sleep. Astronauts obtained significantly more sleep immediately post-flight. The increase seen in sleep duration post-flight may indicate a sleep debt accrued on orbit.
  • Circadian desynchrony seems to occur on ISS. Estimates of circadian phase were generated by the validated model in the Circadian Performance Simulation Software [3]. The model provides a predicted body temperature minimum (PTM) based on the sleep-wake data and found that sleep on 21% of nights on ISS occurred outside of the PTM.
  • Sleep and was significantly reduced when it occurred outside of the PTM (4.77 hours average compared to 6.04 hours).  
  • In addition, astronauts reported taking sleep medication on 11% of nights when the PTM was aligned and on 28% of nights when the PTM was misaligned.

These findings therefore address Gap Sleep 3, by demonstrating that sleep loss does continue on long duration spaceflight (specifically, ISS). Furthermore, this study indicates that circadian desynchronization does occur on orbit. While there was no specific formal assessment of workload conducted, it is well known in the NASA community that workload remains high on ISS missions.

 

While we believe this task addresses the gap at hand, it should be acknowledged that the gap’s “yes-no” verbiage lends itself to closure. The findings from this investigation do beget more questions, such as why? What is the relative contribution of various environmental and mission stressors to continued sleep loss and circadian misalignment? Based on this understanding, what are operationally-relevant recommendations and requirements that can be brought forth to habitat designers, mission planners and medical operations personnel?  The Sleep-Wake investigation and others [2, 4] have sought to understand from crewmembers their assessment of why they feel sleep was reduced in space. In addition, a recent study in a long duration spaceflight analog [5] further demonstrated that circadian misalignment and sleep loss may remain a threat during exploration.

 

A more systematic and comprehensive assessment of factors salient to the astronaut, as well as factors that may not be as obvious, is needed. These subsequent efforts will now be addressed via Sleep Gap 10:  ”We need to identify the spaceflight environmental and mission factors that contribute to sleep decrements and circadian misalignment, and their acceptable levels of risk”, as well as other gaps carried in our Behavioral Medicine and Team Risks.

 

[1] Whitmire, A., Leveton, L., Barger, L., Brainard, B., Dinges, D., Klerman, E., and Shea, C. (2008). Risk of performance errors due to sleep loss, circadian desynchronization, fatigue, and work overload. In: McPhee J, Charles JB, eds. Human Health and Performance Risks of Space Exploration Missions. NASA SP-2009-3405:85-116.

 

 

 

[2] Czeisler, C., Barger, L., Wright, K., Ronda, J., Evans, E. (2012). Sleep-Wake Actigraphy and Light Exposure During Spaceflight. Preliminary report.

 

 

 

[3] Flynn-Evans, E., Barger, L., Kubey, A., Wright, K., Klerman, E., and Czeisler, C. (2013). Sleep Duration and Medication Use Among Astronauts During Predicted Circadian Misalignment on Long Duration Missions Aboard the International Space Station. Abstracted presented at the NASA Human Research Program Investigator’s Workshop, February 13, 2013. http://www.hrpiws2013.com/abstractPDF/2012-12-17Flynn-EvansHRP.pdf

 

 

 

[4] Whitmire, A., Slack, K., Locke, J., Keeton, K., Patterson, H., Faulk, J., Leveton, L. (2013). Sleep Quality Questionnaire: Short Duration Flyers. NASA Technical Memorandum (in press).

 

[5] Basner, M., Dinges, D. F., Mollicone, D., Ecker, A., Jones, C. W., Hyder, E. C., ... & Sutton, J. P. (2013). Mars 520-d mission simulation reveals protracted crew hypokinesis and alterations of sleep duration and timing. Proceedings of the National Academy of Sciences, 110(7), 2635-2640.


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Description

This knowledge gap as addresses the need to characterize the nature of sleep, circadian desynchronization, extended wakefulness and work overload, over the course of a long duration mission in space. Anecdotal reports indicate that many crew members often do not sleep for the duration of their scheduled sleep period. Causes of reduced sleep may be due to mission requirements, which require shifts in sleep/wake schedules, and various environmental factors, such as noise levels and temperature. In order to assess accurately the degree to which sleep is disrupted, and the degree to which circadian shifting, work overload and extended wakefulness occur in flight, objective measures are needed. 

 

The Actiwatch protocol currently on Shuttle and ISS serves as a research monitoring tool, collecting sleep data throughout the course of a mission; this measure also provides important operational feedback for flight surgeons regarding crew member sleep. More precise monitoring tools that provide useful feedback in real time are needed to optimally support teams in future missions.

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Risk Risk of Performance Decrements and Adverse Health Outcomes Resulting from Sleep Loss, Circadian Desynchronization, and Work Overload
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