Cosmic Radiation May Accelerate Onset Of Alzheimer's
January 1, 2013

Astronauts Exposed To Cosmic Rays At Greater Risk Of Alzheimer’s Disease

April Flowers for - Your Universe Online

Space travel is fraught with dangers for astronauts and equipment alike. A new study, led by the University of Rochester Medical Center, reveals that it may be much more dangerous than previously thought. The findings, published in the journal PLOS ONE, show that cosmic radiation — which would bombard astronauts on deep space missions — could accelerate the onset of Alzheimer's disease.

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

The earth's magnetic field protects the planet and people in low earth orbit from the particles of radiation. Once astronauts leave orbit, however, they are exposed to a constant shower of various radioactive particles. If they have appropriate warning, astronauts can be shielded from the radiation of solar flares, but there are other forms of cosmic radiation that cannot be effectively blocked.

The longer a deep space mission, the more exposure the astronauts have to these low levels of radiation. This is becoming of greater concern as NASA plans manned missions to a distant asteroid in 2021 and to Mars in 2035. The round trip to Mars could take as long as three years, making the exposure to radiation intense.

NASA has been funding research into the potential health risks of space travel for over 25 years in an effort to both develop countermeasures and determine whether the risks outweigh the gains from extended missions in deep space.

Several previous studies have revealed the potential cancer, cardiovascular, and musculoskeletal impact of cosmic radiation. The new study is the first to examine the potential impact of that radiation on neurodegeneration — particularly the processes in the brain that contribute to the development of Alzheimer's disease. For the last eight years, O'Banion and his team — whose research focuses on how radiation affects the central nervous system — have been working with NASA.

The team looked at the impact of a particular form of cosmic radiation called high-mass, high-charged particles (HZE). Propelled through space at very high speeds by the force of exploding stars, HZE particles come in many forms. Iron particles were chosen for this study. HZE particles like iron have a greater mass than hydrogen protons produced by solar flares. This mass, combined with their speed, enables the particles to penetrate solid objects like the wall and protective shielding of a spacecraft.

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

The research was partially conducted at the NASA Space Radiation Laboratory at Brookhaven National Laboratory. Brookhaven has particle accelerators which — by colliding matter together at very high speeds — are able to reproduce the radioactive particles found in space, leading NASA to locate its research operations there.

The aim of the research was to examine whether or not radiation exposure had the potential to accelerate the biological and cognitive indicators of Alzheimer's disease, especially in those who may be predisposed to developing the disease. The team chose to study the impact on animal models of Alzheimer's disease that have been extensively studied, allowing scientists to understand the precise timeframe in which the disease should progress over time.

Animals at Brookhaven were exposed to varying doses of radiation, including levels comparable to what astronauts would experience during a mission to Mars. Meanwhile, researchers at Rochester evaluated the cognitive and biological impact of the exposure. In a series of experiments in which mice had to recall objects or specific locations, the team observed that mice exposed to radiation were far more likely to fail at these tasks earlier than the typical appearance of such symptoms. This suggests neurological impairment.

There were also vascular alterations and a greater than normal accumulation of beta amyloid, the protein "plaque" that accumulates in the brain and is one of the hallmarks of the disease, in the brains of the mice.

"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."