Responsible Center: NSBRI
Solicitation: 2015-16 HERO NNJ15ZSA001N-Crew Health (FLAGSHIP, NSBRI, OMNIBUS). Appendix A-Crew Health, Appendix B-NSBRI, Appendix C-Omnibus
Grant/Contract No.: NCC 9-58-HFP04502
Project Type: GROUND
No. of Post Docs: 0
No. of PhD Candidates: 0
No. of Master's Candidates: 0
No. of Bachelor's Candidates: 3
No. of PhD Degrees: 0
No. of Master's Degrees: 0
No. of Bachelor's Degrees: 0
|| BACKGROUND: After landing on the moon in 1969, Astronaut Neil Armstrong was reportedly unable to sleep all night and Astronaut Buzz Aldrin managed only a couple of hours of fitful drowsing during their 21.6 hours on the moon, reportedly because they could not escape from light and noise in the small cabin of their spacecraft and the spacesuit's cooling system made it too cold for sleeping. Environmental factors continue to impact sleep in the modern era of spaceflight.
During a ten-year study of sleep aboard Shuttle and International Space Station (ISS) missions, crewmembers reported sleep disturbances via a daily log. Shuttle crewmembers reported sleep disturbance on 58 percent of inflight nights and ISS crewmembers reported sleep disturbance on 35 percent of inflight nights. There are numerous stressors that are unique to the spaceflight environment that might account for sleep disturbances and prompt use of sleep-promoting medications. Noise, which can disrupt slow wave and REM sleep, both of which are critical to the restorative function of sleep, remains a major source of sleep disruption in modern spaceflight. Both shuttle and ISS crewmembers attributed 1 in 5 inflight disruptions to noise. Although not included in the daily diary of the previous study due to its insidious nature, low levels of oxygen and high levels of carbon dioxide have been hypothesized to account for sleep disturbances during spaceflight.
METHODOLOGY: Over the past ten years, we objectively assessed, via wrist actigraphy and daily logs, sleep-wake timing of 64 astronauts on 80 Space Shuttle missions, encompassing 26 Space Transportation System flights (1,063 inflight days), and 21 astronauts on the ISS (3,248 inflight days). Thus, we have a database of over 4,000 sleep episodes, which provides a unique opportunity to objectively analyze other environmental factors that may influence sleep during spaceflight. Our research team included NASA investigators and operational personnel who have collected time-stamped environmental data during spaceflight (e.g., noise levels, oxygen and carbon dioxide levels). We statistically evaluated the association among objective and subjective measures of sleep quantity and quality with varying levels of these environmental factors.
RESULTS: None of the sleep variables showed any significant difference between the 14.7 psia and 10.2 psia conditions. There was a significant increase (22 minutes) in total sleep time (TST) when the mean ppCO2 was = 4 mmHg (t=2.62, p=0.01). When controlling for age, gender, and the reported use of sleep-promoting medications, one mmHg increase in the mean partial pressure of oxygen was associated with an increase of 58.8 minutes of TST (p<0.001), a 4.3% increase in sleep efficiency (SE) (p=0.01), an increase 62.1 minutes in somatic symptom disorder (SSD) (p=0.0004) and a 15.3 unit increase in sleep quality (SQ) (p=0.0008). One mmHg increase in the mean ppCO2 was associated with a decrease of 8.8 minutes of TST (p<0.001) and a decrease of 7.4 minutes in SSD (p=0.009). There were no personal acoustic dosimetry recordings at or above 80dBA during actigraphy-defined main sleep episodes; 94% of dosimetry recorded during main sleep episodes were less than 60dBA.
CONCLUSIONS: Environmental factors, such as hypoxia and hypercapnia impact sleep during spaceflight. The collection of environmental data should continue with coordination between the life science and environmental teams so that the data that is collected will have the necessary detail to be usable by both groups. This coordinated research approach could have a substantial impact on countermeasures, interventions and/or policies affecting spaceflight crewmembers in an effort to improve their health, performance, and safety.
|Research Impact/Earth Benefits:
|| We investigated whether noise, hypoxia, and hypercapnia were associated with sleep deficiency during spaceflight. The results of this research have major implications for all operational personnel who are required to sleep under less than ideal environmental conditions, such as military personnel. The results of this work could lead to further guidance, policies, and/or countermeasures to improve sleep during spaceflight missions and on Earth.