Physiological Threats to Mental Health in Long-Term Space Mission
The previous writing assignment covered current research on the psychological well-being of astronauts in a proposed long-term space mission. Social and behavioral factors like stress, mood-states, and sleep deprivation were the main threats to the mental health of astronauts. However, another side to this discussion includes the physical and medical effects on mental health from ever-present physiological dangers.
On Earth, CO2 typically constitutes 0.03% of air by volume. On space habitats like the ISS, ventilation of air and air composition are controlled, and are not always perfect. CO2 levels on the ISS are about 0.5%(+/-0.2%), following NASA’s Spacecraft Maximum Allowable Concentration of 0.7% CO2. However, larger variations in CO2 concentration, from poor air-flow in certain regions of the ISS to unexpected increases as a result of exercise or a larger congregation of astronauts in one area, can pose an actual risk (Stankovic, 2016).
In one study, 22 participants were given cognitive tests under 3 levels of CO2 concentration, 0.06% (600ppm), 0.1% (1000 ppm) and 0.25% (25,000 ppm). Figure 1 shows the results of the study in 9 graphs, each focusing on a component of the tests. In “task orientation,” “initiative,” “basic strategy,” and “breadth of approach,” there are clear deviations in the performance of the group under the 3 levels of CO2 concentration (Satish et al., 2012).
Figure 1: Nine graphs displaying the data of the 22-participant cognitive test, with the three CO2 levels in different colors and points, participant on the x-axis, and score on the y-axis. Each of the nine graphs focuses on a component of the tests.
Though CO2 concentration poses a recognizably legitimate danger in higher-than-normal levels, less research has been done on whether microgravity has a direct affect on the cognition of astronauts. However, one study compared the hippocampal CA1 neurons of rats before and after exposure to 14 days of simulated microgravity (Ranjan et. al, 2014). The study found that the mean area, perimeter, synaptic cleft, and length of the CA1 neurons in the rats all significantly decreased after the simulated microgravity. It concluded that these deteriorations could have a great effect on the learning and memory ability of astronauts, two key cognitive qualities of being an efficient astronaut.
Figure 2: A diagram showing the relationship between radiation exposure during a space mission and the subsequent psychological risk. BHP stands for NASA’s Behavioral Health and Performance program.
Another less-thought-of cause for ill mental health in space, and with less astronaut-based research, is radiation. Figure 2 shows an indirect path from small exposures to radiation to nervous system damage and effects on behavioral health (Slack, 2016).
One study exposed Fischer 344 and Lewis rats to 25 and 100 cGy of proton radiation, performed rPVT tests for rodent cognition and memory, and analyzed certain proteins of their brains after 9 months. The study found that although the the rats exposed to the two levels of proton radiation demonstrated lower accuracy and higher impulsive responding, they did not have rPVT scores that were statistically different from the control group. However, the rats exposed to radiation had significantly smaller frontal cortex proteins and cytokine arrays than the control group, and the baseline dopaminergic functions of the rats were responsible for recovery from the radiation damage (Davis et al., 2015).
Works Cited
Davis, Catherine M., Kathleen L. DeCicco-Skinner, Robert D. Heinz. “Deficits in Sustained Attention and Changes in Dopaminergic Protein Levels following Exposure to Proton Radiation Are Related to Basal Dopaminergic Function.” PLOS ONE. 10, no. 12 (December, 2015) [Cited 20 November 2016].
Ranjan, Amit, Jitendra Behari, Birenda N. Mallick. “Cytomorphometric changes in hippocampal CA1 neurons exposed to simulated microgravity using rats as model.” Frontiers in Neurology. 5 (May, 2014) [Cited 20 November 2016].
Satish, Usha, Mark J. Mendell, Krishnamurthy Shekar, et al. “Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance.” Environmental Health Perspectives. 120, no. 12 (December, 2012) [Cited 20 November 2016].
Slack, Kelley J., Thomas J. Williams, Jason S. Schneiderman, et al. “Evidence Report: Risk of Adverse Cognitive or Behavioral
Conditions and Psychiatric Disorders.” (19) National Aeronautics and Space Administration. (April, 2016) [Cited 20 November 2016]
Stankovic, Aleksandra, David Alexander, Charles M. Oman, et al. “A Review of Cognitive and Behavioral Effects of
Increased Carbon Dioxide Exposure in Humans.” (2-3) National Aeronautics and Space Administration. (August, 2016) [Cited 20 November 2016]
