Concussions and other traumatic brain injuries may increase the risk of developing Alzheimer’s disease earlier in life, according to a study published in Neuropsychology.
The research – the first to use autopsy-confirmed cases of Alzheimer’s disease to examine the long-term effects of head injuries – supports a correlation that could only be speculated about in previous studies, which lacked definitive diagnostic methods.
An analysis of more than 2,100 cases found that people who sustained traumatic brain injury (TBI) with loss of consciousness greater than five minutes were diagnosed with dementia on average two and a half years earlier than those who had not experienced TBI.
The study differs from previous studies on the degree of the association, with some reporting TBI history can accelerate onset of Alzheimer’s by up to nine years and other research finding no relationship between the two. However, those studies used less definitive methods to diagnose dementia, which raises the possibility they included data from patients who didn’t have Alzheimer’s disease.
More research is needed to answer several questions not addressed by the new findings, such as specifically what happens during a TBI that might contribute to dementia later in life for some individuals, what other factors play a role, and who is most susceptible. Scientists speculate that inflammation occurs in the brain following a TBI, which may set the stage for the later development of neurodegeneration, and that other genetic factors and unknown triggers or risk factors are probably involved.