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How many concussions does it take to lead to Alzheimer's disease?

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Are concussions related to Alzheimer's disease? You're eight years old on the playground and the kid next to you gives you a shove. You fall and hit your cheek on the ground and are knocked unconscious for a few seconds. You wake up and then begin to throw up. The next day, you're back at school after a mild concussion. Has the boy next door who gave you that unexpected shove to the ground now caused you to get Alzheimer's disease years later?

How many concussions does it take to lead to Alzheimer's disease? Some studies say it may take more than one concussion. Research seems to indicate that more than one concussion can cause a person to have early onset dementia and other similar disorders, and three or more concussions can cause a person, particularly an athlete, to be five times more likely to suffer from early-onset Alzheimer's disease, according to the article, "What's the link between concussions and brain health?"

A new study suggests that a history of concussion involving at least a momentary loss of consciousness may be related to the buildup of Alzheimer's-associated plaques in the brain. The research, "Head trauma and in vivo measures of amyloid and neurodegeneration in a population-based study," is published in the December 26, 2013, online issue of Neurology®, the medical journal of the American Academy of Neurology.

"Interestingly, in people with a history of concussion, a difference in the amount of brain plaques was found only in those with memory and thinking problems, not in those who were cognitively normal," said study author Michelle Mielke, PhD, with Mayo Clinic in Rochester, Minnesota, according to the December 26, 2013 news release, "Are concussions related to Alzheimer's disease?"

For the study, people from Olmsted County in Minnesota were given brain scans; these included 448 people without any signs of memory problems and 141 people with memory and thinking problems called mild cognitive impairment. Participants, who were all age 70 or older, were also asked about whether they had ever experienced a brain injury that involved any loss of consciousness or memory.

Of the 448 people without any thinking or memory problems, 17 percent reported a brain injury and 18 percent of the 141 with memory and thinking difficulties reported a concussion or head trauma

The study found no difference in any brain scan measures among the people without memory and thinking impairments, whether or not they had head trauma. However, people with memory and thinking impairments and a history of head trauma had levels of amyloid plaques an average of 18 percent higher than those with no head trauma history.

"Our results add merit to the idea that concussion and Alzheimer's disease brain pathology may be related," said Mielke in the news release. "However, the fact that we did not find a relationship in those without memory and thinking problems suggests that any association between head trauma and amyloid is complex."

The study was supported by the National Institutes of Health, the Robert Wood Johnson Foundation, the Alexander Family Alzheimer's Disease Research Professorship, GE Healthcare, the Elsie and Marvin Dekelboum Family Foundation, the MN Partnership for Biotechnology and Medical Genomics and the Robert H. and Clarice Smith and Abigail van Buren Alzheimer's Disease Research Program. To learn more about concussion, please visit the AAN Concussion information site. To learn more about Alzheimer's disease, please visit the AAN informational site for patients.

The American Academy of Neurology, an association of more than 26,000 neurologists and neuroscience professionals, is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer's disease, stroke, migraine, multiple sclerosis, brain injury, Parkinson's disease and epilepsy.

You may also be interested in another study, "Neurologic diseases in ancient Roman sculpture busts." Or check out the abstract of this other study, "High total cholesterol levels in late life associated with a reduced risk of dementia." Check out another study's abstract, "Neurodegenerative causes of death among retired National Football League players."



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