Researchers from the University of Bordeaux explored how different gravity levels affect human sleep by studying microgravity and hypergravity conditions. Their findings indicate that sleep quality declines when gravity deviates from normal Earth gravity, especially in zero gravity and similar altered states, compared with typical gravity. The study appears in the Journal of Sleep Research, a peer reviewed publication that compiles sleep science from around the world.
The investigation centered on participants who took part in parabolic flights, a method used to recreate brief periods of microgravity and higher gravity for of research and training purposes.
In total, three parabolic flight sessions were conducted between October 2022 and April 2023. Prior to and after these flights, participants wore actigraphy devices—wrist worn monitors that track movement to infer sleep patterns and restfulness. The data from these devices provided objective insight into how often sleep was interrupted and how long participants stayed asleep across different gravity states.
Each parabola began with a hypergravity phase, exposing participants to roughly 1.8 times Earth’s gravity for about 20 seconds. This was followed by a microgravity phase lasting around 22 seconds. The alternating forces created a rapid, repeated shift in sensory input, challenging the body’s usual sleep regulation mechanisms.
Analysis showed that sleep tended to be more fragmented on the night after a parabolic flight compared with the night before. In practical terms, participants experienced more awakenings and shorter continuous sleep periods following exposure to the gravity transitions.
Interestingly, the subjective reports from participants often indicated that they slept well after completing the flights. This discrepancy between objective measures of sleep fragmentation and subjective sleep satisfaction is a notable finding in the study design, suggesting a possible mismatch between how sleep is experienced and how it is perceived after such experiences.
Scientists offer a potential explanation for this paradox. The positive emotional experiences associated with parabolic flights, including the novelty and excitement of the activity, may improve overall mood and personal impressions of the testing period. This emotional uplift could influence participants to report better sleep quality despite objective signs of fragmentation, highlighting the difference between mood influenced assessments and physiological measurements in sleep research. In other words, mood and memory of the experience can color self reported sleep quality, even when actigraphy indicates disruptions in sleep continuity.
Previous research has suggested gender differences in how space related stress is managed. In this study, researchers note that women have shown better resilience in space environments in some prior work, while men can face different sleep related challenges. The current results add to a growing body of evidence examining how biological and psychological factors intersect in extreme environments, and they underscore the value of including a diverse participant pool in sleep research that involves unusual gravity conditions. The findings contribute to a broader understanding of how the human body responds to gravitational changes and how such responses might be managed or mitigated in future spaceflight training and planning. The work also reinforces the importance of pairing objective sleep assessment with subjective reports to gain a fuller picture of sleep health under extraordinary conditions. This combined approach helps researchers build practical guidelines for maintaining sleep quality in astronauts and others who encounter nonstandard gravity scenarios, and it aligns with ongoing efforts to optimize crew well being during extended missions. [JSR citation]