Mars 520-d mission simulation reveals protracted crew hypokinesis and alterations of sleep duration and timing

Abstract

The success of interplanetary human spaceflight will depend on many factors, including the behavioral activity levels, sleep, and circadian timing of crews exposed to prolonged microgravity and confinement. To address the effects of the latter, we used a highfidelity ground simulation of a Mars mission to objectively track sleep-wake dynamics in a multinational crew of six during 520 d of confined isolation. Measurements included continuous recordings of wrist actigraphy and light exposure (4.396 million min) and weekly computer-based neurobehavioral assessments (n = 888) to identify changes in the crew's activity levels, sleep quantity and quality, sleep-wake periodicity, vigilance performance, and workload throughout the record-long 17 mo of mission confinement. Actigraphy revealed that crew sedentariness increased across the mission as evident in decreased waking movement (i.e., hypokinesis) and increased sleep and rest times. Light exposure decreased during the mission. The majority of crewmembers also experienced one or more disturbances of sleep quality, vigilance deficits, or altered sleep-wake periodicity and timing, suggesting inadequate circadian entrainment. The results point to the need to identify markers of differential vulnerability to hypokinesis and sleepwake changes during the prolonged isolation of exploration spaceflight and the need to ensure maintenance of circadian entrainment, sleep quantity and quality, and optimal activity levels during exploration missions. Therefore, successful adaptation to such missions will require crew to transit in spacecraft and live in surface habitats that instantiate aspects of Earth's geophysical signals (appropriately timed light exposure, food intake, exercise) required for temporal organization and maintenance of human behavior.sleep-wake regulation | astronaut T he success of human interplanetary spaceflight, which is anticipated to be in this century, will depend on the ability of spacefarers to remain confined and isolated from Earth much longer than previous missions or simulations, while maintaining the intensity and timing of behavioral activity necessary to accomplish the mission and mitigate the effects of microgravity. A total of four people have spent >1 y in space, with the record of 437 consecutive days on the Mir space station set by Valery Polyakov. The longest Earth-based spaceflight simulation involved four Russians confined in connected hyperbaric chambers for 240 consecutive days. Antarctic winter-over missions have extended up to 363 d. Prediction of how prolonged confinement affects activity levels and sleep-wake dynamics of space explorers is needed to inform spacecraft habitability requirements, crew selection, and behavioral countermeasures during interplanetary missions (1-3). To address this need, we obtained objective neurobehavioral data on the activity patterns of a multinational, culturally diverse crew of six males with backgrounds in engineering, medicine, physiology, and space training, who participated in a high-fidelity g...

Effects of Sex and Gender on Adaptation to Space: Behavioral Health

“…The majority of crew members developed disturbances of sleep and other behavioral changes that would be undesirable in long-duration space missions. 64 This finding leaves unresolved how female participants would have fared in this Mars mission analog. There is a compelling need for more research on how to optimize the behavioral health of both women and men in spaceflight to ensure their performance and the likelihood of continued successful missions of longer duration and of greater autonomous operations.…”

Temporal dynamics of the gut microbiota in people sharing a confined environment, a 520-day ground-based space simulation, MARS500

“…Indeed, the overall increased relative abundance of Bacteroides species in all subjects in the very first stage of the mission, which had already been experienced by astronauts during the Skylab Medical Experiments Altitude Test (SMEAT) in a 56-day confinement study in 1975, and explained by the authors as a possible consequence of a stress situation is noteworthy [19]. Interestingly, early in the MARS500 mission, almost all crewmembers experienced one or more individual-specific disturbances of sleep quality, vigilance deficits, or alterations in sleep-wake timing and periodicity [20], suggesting a differential, but still stressful, context. Bacteroides is a major producer of propionate as well as phenolic acids, which are associated with benefits for human health [21].…”

Psychological and Behavioral Changes during Confinement in a 520-Day Simulated Interplanetary Mission to Mars

“…Although we could have justified many different hypotheses relative to time in mission (e.g., steadily increasing or decreasing effects, third quarter effect), we chose to keep our hypothesis as generic as possible (null hypothesis: no difference between mission quarters). This was partially driven by findings on the activity data that showed a steep decline in activity initially, a slow but steady decline during the second and third mission quarters, and a sharp rise at the end of the mission, which conformed to neither of the two above-stated hypotheses [19]. Our mixed model analyses took the clustered nature of the data into account and used all available data points based on repeated measures within subjects (N = 444 for measures sampled only in the morning or in the evening and N = 888 for measures sampled both in the morning and the evening).…”