Comments on “Prolonged Microgravity Affects Human Brain Structure and Function”

This letter addresses the article, “Prolonged Microgravity Affects Human Brain Structure and Function.”¹ To investigate whether brain structural changes (which can be observed after long-term space missions) are associated with alterations in motor or cognitive function, Roberts et al¹ retrospectively analyzed brain MR images of National Aeronautics and Space Administration astronauts to quantify pre- to postflight alterations in brain structure. They showed that brain structural changes were linked to changes in cognitive and motor test scores as well as the development of spaceflight-associated neuro-optic syndrome. However, due to the small sample size and number of comparisons, they suggested that their findings should be interpreted with cautioun.

Although this article has certain strengths, it has at least 1 major shortcoming that stems from ignoring the key point that in long-duration deep space missions, astronauts are exposed to multiple stressors ranging from psychological stress due to the confined environment to ionizing radiation and gravitational changes. It is not well-understood whether these stressors impact the central nervous system only individually or in combination (ie, synergistically). However, what we are fully aware of is the key role of space radiation on human brain function, according to Parihar et al,² “The Mars mission will result in an inevitable exposure to cosmic radiation that has been shown to cause cognitive impairments in rodent models, and possibly in astronauts engaged in deep space travel.” Cucinotta et al³ have also confirmed galactic cosmic ray (GCR)-induced alterations in astronauts’ cognitive function, “Galactic cosmic rays may alter astronauts, cognition during space missions.” Cucinotta et al also reported that exposure to GCRs can be associated with increased risk of CNS disorders, “GCR[s] may increase central nervous system risks including Alzheimer disease.” Most important, Krukowski et al⁴ reported that novel pharmaceutical agents are being explored for their ability to protect memory function in rodents exposed to simulated cosmic radiation, “Now neuroscientists have identified a potential treatment for the brain damage caused by cosmic rays, a drug that prevents memory impairment in mice exposed to simulated space radiation.” In summary, this omission has possibly affected the validity of the findings of the study conducted by Roberts et al.¹

• © 2020 by American Journal of Neuroradiology