Circadian misalignment affects sleep and medication use before and during spaceflight

Abstract

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 (n=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 (P<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, P<0.01). Sleep-promoting medication use was significantly higher during misaligned (24%) compared with aligned (11%) sleep episodes (P<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%; P<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.

Long-Term Microgravity Effects on Isometric Handgrip and Precision Pinch Force with Visual and Proprioceptive Feedback

“…Our results are in accordance with previous NASA studies that demonstrate International Journal of Aerospace Engineering that even bones are affected over the course of long-term missions by loss of their total hip bone mass [14]. Moreover, our data add information to the list of known effects of space flights on the human body during long-duration missions such as muscle atrophy, bone demineralization, altered immune function [15,16], cardiovascular system dysfunction [17,18], and also alterations in sleep function [19]. A significant amount of data on the decrease in the performance of various groups of muscles has been collected from astronauts flying from 1989 to 1995 in NASA's orbiters or Russian capsules [20].…”

Nucleic acid detection aboard the International Space Station by colorimetric loop‐mediated isothermal amplification (LAMP)

“…Aberrant regulation of telomere length has been associated with a number of human diseases and the link between physiological stress and aberrant regulation of telomere length is well documented . Stresses astronauts experience during spaceflight have been also shown to lead to alterations in telomere dynamics . For example, the NASA Twins Study found that the average telomere length in astronaut Scott Kelly's white blood cells increased over the course of his mission and returned to the pre‐flight length after his return to Earth .…”

“…[27][28][29] Stresses astronauts experience during spaceflight have been also shown to lead to alterations in telomere dynamics. 5,[30][31][32][33] For example, the NASA Twins Study found that the average telomere length in astronaut Scott Kelly's white blood cells increased over the course of his mission and returned to the pre-flight length after his return to Earth. 5 It is hypothesized that changes in telomere length during spaceflight, such as those observed in Scott Kelly, may lead to tissue-specific molecular and cellular responses.…”

Ergonomic Challenges for Astronauts during Space Travel and the Need for Space Medicine

“…On Earth, humans have evolved a circadian rhythm based upon a 24 hour lightdark cycle and a gravitational force of 1 x g. Sleep quantity and quality are both negatively affected during spaceflight and the use of medication to promote sleep is prevalent, especially as astronauts are required to execute part of the mission where there is misalignment to the circadian rhythm, brought about by vehicle launch, orbit and docking times [6,[25][26][27]. Impairment of cognitive ability may be a concern and at worst constitute risk at the task or entire mission level with potentially life-threatening consequences.…”