The study, published in the journal Neurology, found 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.
Study author Michelle Mielke of the Mayo Clinic in Rochester, Minn., said the study involved people from Olmsted County in Minnesota, who were given brain scans, including 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 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, while 18 percent of the 141 with memory and thinking difficulties reported a concussion or head trauma, the study said.
The study found no difference in any brain scan measures among those without memory and thinking impairments, whether or not they had head trauma, but those with cognition and memory problems had higher levels of amyloid plaques.
"Our results add merit to the idea that concussion and Alzheimer's disease brain pathology may be related," Mielke said in a statement. "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."