Circadian misalignment affects sleep and medication use before and during spaceflight

Jul 21, 2017NPJ microgravity

Misaligned body clocks affect sleep and medicine use before and during space travel

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Circadian Biology on OpenScience ↗PubMed ↗DOI ↗OA ↗

Abstract

The estimated endogenous circadian temperature minimum occurred outside sleep episodes on 19% of sleep episodes during spaceflight.

Mean sleep duration was 6.4±1.2 hours during aligned sleep episodes and 5.4±1.4 hours during misaligned episodes.
Astronauts reported significantly better sleep quality during aligned episodes (66.8±17.7) than during misaligned episodes (60.2±21.0).
Sleep-promoting medication use was significantly higher during misaligned sleep episodes (24%) compared to aligned episodes (11%).
Use of any medication was significantly higher on days with misaligned sleep episodes (63%) versus aligned days (49%).
Circadian misalignment is associated with sleep deficiency and increased medication use during spaceflight.

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Sleep deficiency and the use of sleep-promoting medication are prevalent during spaceflight. Operations frequently dictate work during the biological night and sleep during the biological day, which contribute to circadian misalignment. We investigated whether circadian misalignment was associated with adverse sleep outcomes before (preflight) and during spaceflight missions aboard the International Space Station (ISS). Actigraphy and photometry data for 21 astronauts were collected over 3,248 days of long-duration spaceflight on the ISS and 11 days prior to launch (=231 days). Sleep logs, collected one out of every 3 weeks in flight and daily on Earth, were used to determine medication use and subjective ratings of sleep quality. Actigraphy and photometry data were processed using Circadian Performance Simulation Software to calculate the estimated endogenous circadian temperature minimum. Sleep episodes were classified as aligned or misaligned relative to the estimated endogenous circadian temperature minimum. Mixed-effects regression models accounting for repeated measures were computed by data collection interval (preflight, flight) and circadian alignment status. The estimated endogenous circadian temperature minimum occurred outside sleep episodes on 13% of sleep episodes during preflight and on 19% of sleep episodes during spaceflight. The mean sleep duration in low-Earth orbit on the ISS was 6.4±1.2 h during aligned and 5.4±1.4 h (<0.01) during misaligned sleep episodes. During aligned sleep episodes, astronauts rated their sleep quality as significantly better than during misaligned sleep episodes (66.8±17.7 vs. 60.2±21.0,<0.01). Sleep-promoting medication use was significantly higher during misaligned (24%) compared with aligned (11%) sleep episodes (<0.01). Use of any medication was significantly higher on days when sleep episodes were misaligned (63%) compared with when sleep episodes were aligned (49%;<0.01). Circadian misalignment is associated with sleep deficiency and increased medication use during spaceflight. These findings suggest that there is an immediate need to deploy and assess effective countermeasures to minimize circadian misalignment and consequent adverse sleep outcomes both before and during spaceflight. n P P P P

Key numbers

19%

Circadian Misalignment Rate

Percentage of sleep episodes misaligned during spaceflight.

1 h

Average Sleep Duration Decrease

Average sleep loss when episodes were misaligned vs. aligned.

24%

Medication Use Increase

Percentage of sleep episodes using medication during misaligned sleep.

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Circadian misalignment affects sleep and medication use before and during spaceflight

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