Long exposure to cosmic rays may cause dementia and cognitive impairments, study reveals

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KnowledgeGlue

UCI study reveals that galactic cosmic rays may cause brain damage after prolonged exposure, raising concerns regarding future interplanetary spaceflights.

It has only been two weeks since Elon Musk unveiled his ambitious plan to colonize Mars, and the list of practical issues to be solved before we officially set out on an interplanetary journey has already grown. We are talking about galactic cosmic rays, a phenomenon that we have been aware of for a long time, but one that we have never addressed. Musk has even acknowledged that they may increase the risk of cancer, but a definite answer to the problem has yet to arrive.

Now, researchers from the University of California, Irvine have demonstrated that prolonged exposure to highly energetic charged particles – much like the cosmic rays that astronauts will be bombarded by on their journey to Mars and beyond – causes significant long-term brain damage in test rodents, resulting in cognitive impairments and dementia.

In other words, astronauts may not even remember much of their journey, and their cognitive abilities and mental health will suffer greatly, and potentially permanently.

“The space environment poses unique hazards to astronauts. Exposure to these particles can lead to a range of potential central nervous system complications that can occur during and persist long after actual space travel – such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making. Many of these adverse consequences to cognition may continue and progress throughout life,” said Charles Limoli, the professor of radiation oncology in UCI’s School of Medicine.

For the study, rodents were subjected to charged particle irradiation (fully ionized oxygen and titanium) at the NASA Space Radiation Laboratory at New York’s Brookhaven National Laboratory and then sent to Limoli’s UCI lab. Limoli’s work is part of NASA’s Human Research Program. Investigating how space radiation affects astronauts and learning ways to mitigate those effects are critical to further human exploration of space.

Six months after exposure, the researchers still found significant levels of brain inflammation and damage to neurons. Imaging revealed that the brain’s neural network was impaired through the reduction of dendrites and spines on these neurons, which disrupts the transmission of signals among brain cells. These deficiencies were parallel to poor performance on behavioral tasks designed to test learning and memory.

But it doesn’t end there. Limoli and his colleagues have revealed that the radiation also affected “fear extinction”, an active brain process that continuously supresses prior negative or stressful associations, as when someone who nearly drowned learns to enjoy water again. A deficit in such a major mental defense mechanism could make a person prone to anxiety and depression, i.e. the last thing you want to see in interplanetary pioneers, who may already be staring death in the face every step of the way.

Though dementia-like deficits in astronauts would take months to manifest, he said, the time required for a mission to Mars is sufficient for such impairments to develop. People working for extended periods on the International Space Station, however, do not face the same level of bombardment with galactic cosmic rays because they are still within the Earth’s protective magnetosphere.

Partial solutions are being explored, Limoli noted. Spacecraft could be designed to include areas of increased shielding, such as those used for rest and sleep. However, these highly energetic charged particles will traverse the ship nonetheless, he added, “and there is really no escaping them.”

Preventive treatments offer some hope. Limoli’s group is working on pharmacological strategies involving compounds that scavenge free radicals and protect neurotransmission.

Break out those tinfoil hats.

Michal Dudic

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