Effects of Head-Down Tilt Bed Rest Plus Elevated CO₂ on Cognitive Performance

Microgravity and elevated CO₂ levels are two important environmental spaceflight stressors that can adversely affect astronaut cognitive performance and jeopardize mission success. This study investigated the effects of 6⁰ head-down tilt bed rest (HDBR) with (N=11 participants, 30 days HDBR) and without (N=8 participants, 60 days HDBR) elevated ambient (3.73 mmHg) CO₂ concentrations on cognitive performance. Participants of both groups performed all 10 tests of NASA's Cognition battery and a brief alertness and mood survey repeatedly before, during, and after the HDBR period. Test scores were adjusted for practice and stimulus set effects. Concentrating on the first 30 days of HDBR, a modest but statistically significant slowing across a range of cognitive domains was found in both groups (Controls: -0.37 SD; 95% CI 0.48, -0.27; adjusted p<0.0001; CO₂: -0.25 SD; 95% CI 0.34, -0.16; adjusted p<0.001), most prominently for sensorimotor speed. These changes were observed early during HDBR and did not further deteriorate or improve with increasing time in HDBR. The study found similar cognitive effects of HDBR irrespective of CO₂ levels, suggesting that elevated CO₂ neither ameliorated nor worsened the HDBR effects. In both groups, cognitive performance after 15 days of recovery was statistically indistinguishable from pre-HDBR performance. However, subjects undergoing 60 days of HDBR rated themselves as feeling more sleepy, tired, physically exhausted, stressed and unhealthy during recovery compared to their 30-day counterparts

Neurostructural, Cognitive, and Physiologic Changes During a 1-Year Antarctic Winter-Over Mission

Exploration-type missions will require humans to live in isolated, confined, and extreme environments for prolonged periods of time. NASA’s Mars Design Reference Mission 5.0 has a duration of 910 days, which is well beyond the duration astronauts and cosmonauts have remained confined in a spacecraft. NASA’s recent evidence-based review of the behavioral health risks to crew and mission success during exploration spaceflight concluded they were among the most serious unmitigated risks to such missions. Due to their complex logistical operations, harsh threatening environmental conditions such as extreme cold, altered photoperiod, low humidity, isolation, and confinement, as well as the analogous population of researchers with multicultural backgrounds, but similar educational background compared to astronauts, Antarctic research stations are considered a high-fidelity analog for long-duration space missions. While NASA and NSBRI have begun collecting some neuroimaging data before and after missions, our knowledge on the effects of prolonged periods in space or space analog environments on neurostructural and neurobehavioral changes is still limited. To address this knowledge gap, we are investigating neurostructural, cognitive, behavioral, physiologic, and psychosocial changes in a total of N=25 crewmembers during two 1-year Antarctic winter-over seasons (2015/2016) in the French/Italian Concordia station. We will assess subjects using quantitative structural and functional magnetic resonance imaging (MRI) before, immediately after (via collaborations with neuroimaging centers in Christchurch, NZ and Hobart, AUS), and 6-months after the winter-over. We will assess Concordia crew members during the mission using sensitive but unobtrusive methods to measure cognitive performance (Cognition test battery [1], monthly), sleep-wake behavior and sleep continuity (actigraphy, continuously [2]), heart rate and heart rate variability (24-h electrocardiography, monthly), relative proximity (actigraphy, continuously), psychomotor vigilance (PVT-B, weekly [3]) and subjective assessments of stress, mood, fatigue, health, workload, monotony, boredom, loneliness, and crewmember conflicts (questionnaires, weekly). A control group with individuals matched to each crewmember according to age and gender will be investigated with similar methodology at the German Aerospace Center (DLR, Cologne). Neuroimaging and Cognition data will also be compared to N=9 crewmembers over-wintering in the German Neumayer-III station in 2015. Furthermore, Cognition data will be compared to 13 crewmembers over-wintering in the British Halley station in 2015. Baseline data collection for both winter-over seasons was finalized in October 2015. Human phantom scans at envihab Cologne, Christchurch, and Hobart were also completed in October 2015. Data acquisition in the first winter-over crew is ongoing with overall good compliance

The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight

To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomere elongation, genome instability, carotid artery distension and increased intima-media thickness, altered ocular structure, transcriptional and metabolic changes, DNA methylation changes in immune and oxidative stress-related pathways, gastrointestinal microbiota alterations, and some cognitive decline postflight. Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted. These multiomic, molecular, physiological, and behavioral datasets provide a valuable roadmap of the putative health risks for future human spaceflight