Older people with a history of concussions or repeated head trauma and memory problems have more buildup of Alzheimer's disease-associated plaques in the brain, according to a study WebMD reported.

Researchers say those with concussion history and cognitive impairment have more amyloid plaques, one of the initial signs of the development of Alzheimer's, than those who had concussion but don't have memory problems.  

 ''What we think it suggests is, head trauma is associated with Alzheimer's-type dementia -- it's a risk factor," Michelle Mielke, study researcher and associate professor of epidemiology and neurology at Mayo Clinic Rochester, is quoted as saying by WebMD. "But it doesn't mean someone with head trauma is [automatically] going to develop Alzheimer's."

In the study, Mielke and her colleagues compared the head trauma history of 141 people who had mild memory loss and cognitive impairment indicative of the development of Alzheimer's disease to the head trauma history of 448 individuals that had no signs of memory loss or cognitive impairment, the Examiner reported.

WebMd reported that of the group without any memory problems, 17 percent had reported a brain injury. Of the group with memory problems, 18 percent did. Mielke stated this study suggests the link between head trauma and the plaques is complex as the proportion of people reporting concussion was the same in both groups.

Brains scans were on all the participants. Researchers found that those who had both concussion history and cognitive impairment had levels of amyloid plaques that were 18 percent higher than those with cognitive impairment but no head trauma history.

Although the researchers cannot claim a cause-and-effect relationship between head trauma and Alzheimer's disease they do indicate a relationship exists between the two.

Mielke stressed that she has found only a link or association, not a cause-and-effect relationship.

The study is published online Dec. 26 and in the Jan. 7 print issue of the journal Neurology.