Space travel may cause early development of Alzheimer’s disease

This Mars photo from ESA's Mars Express spacecraft was taken on Dec. 15, 2012.According to a new study in the journal PLOS ONE, exposure to cosmic radiation on space flights may put astronauts at risk of early-onset Alzheimer's disease.

"Galactic cosmic radiation poses a significant threat to future astronauts," said Dr. M. Kerry O'Banion, a professor at the University of Rochester Medical Center (URMC) Department of Neurobiology and Anatomy, according to Science Daily.

"The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer's disease."

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O'Banion, one of the authors of the PLOS ONE study, and his team have been working with NASA for over eight years, studying the potential effects of radioactive particles on the human central nervous system. When astronauts are outside of the Earth's atmosphere, they have to contend with high radiation levels, but these are manageable due to spacecraft shielding and the Earth's magnetic field. However, once beyond the relative safety of Earth's magnetic field, exposure levels increase and current spacecraft shielding isn't enough to protect against the high-mass, high-energy (HZE) particles in galactic cosmic radiation — atomic nuclei of elements heavier than helium (atomic number of 3 or higher) that were ejected long ago from exploding stars. These HZE particles, such as iron, for example, are fast enough and heavy enough that they can easily pass through current spacecraft shielding.

"Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them," O'Banion said. "One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete."

Using animal models — since they are very well-studied and extremely well-understood — O'Banion and his team studied how radiation levels likely to be experienced by astronauts traveling to Mars would affect the brain, specifically with respect to memory and cognition, two things that are impacted the most by the onset of Alzheimer's disease. Mice were exposed to various doses of radiation, and then tested for their recall of objects and locations. The research team found that those exposed to radiation began to fail these tests earlier than they normally would have in their life-cycle, suggesting a premature impairment of brain function, and they also discovered higher than normal levels of beta amyloid, the protein 'plaque' that builds up in the brain of Alzheimer's sufferers.

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"These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer's disease," said O'Banion. "This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions."

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