A long history of concussions contributes to the build up of Alzheimer's disease, Mayo Clinic researchers found in a new study.

Researchers of the study found that a history of concussions involving at least a momentary loss of consciousness may be related to the build-up of Alzheimer's-associated plaques in the brain.

"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, Minn in a press statement.

Researchers took brain scans of 448 people without any signs of memory problems and 141 people with memory and thinking problems called mild cognitive impairment. Most of the participants were aged 70 years or older. They were also asked to report if they had ever experienced a brain injury that involved any loss of consciousness or memory.

About 17 percent of the people without thinking or memory problems and 18 percent of the people with memory and thinking difficulties reported a concussion or head trauma. Researchers noted no differences in the brain scans of the 448 people.

However, in the other group of people, participants who reported a brain injury had 18 percent higher levels of amyloid plaques than the participants who had no brain injury.

"Our results add merit to the idea that concussion and Alzheimer's disease brain pathology may be related," said Mielke. "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 published in online issue of Neurology.

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