It's well-known that concussions, whether incurred in sports or from an accident or military service (blast wave injury) are dangerous and can have lingering effects. In 96% of professional NFL players, chronic traumatic encephalopathy (CTE) was found in post-mortem examinations.
CTE can cause depression, dementia, angry or impulsive outbursts, anxiety and can contribute to suicidal ideation.
New research from scientists at the University of Texas Southwestern Brain Institute suggests another problem with a brain injury could be an increased risk of developing Alzheimer's disease (AD.) With so much concern in professional sports, youth sports and military service surrounding brain injuries, researchers are looking to understand how a blow to the head could result in earlier onset of dementia.
The research is unique because it's the first time that investigators have used participants who had autopsy-confirmed cases of AD. While Alzheimer's can be diagnosed while patients are still alive, diagnosis is usually made by ruling out other neurological conditions. There are other forms of dementia and brain illness that mimic many of the symptoms of AD, so having it confirmed via autopsy, makes the recent study results more accurate.
The study followed 2,100 cases of where patients had experienced a significant traumatic brain injury (TBI) where they were unconscious for at least five minutes or more. In these individuals, their Alzheimer's disease was diagnosed about 2 ½ years earlier than patients who had never had a head injury.
Dr. Munro Cullum, a neuropsychologist, lead the study and is also involved in a nationwide effort to track injuries that occur in youth sports. Dr. Collum explained, "We need to be aware that brain injury is a risk factor, but parents shouldn't keep their kids out of sports because they fear a concussion will lead to dementia. This is a piece to the puzzle, a step in the direction of understanding how the two are linked."
The work from UT isn't the first study to look at the correlation between TBI history and Alzheimer's, but previous work has been inconclusive. Some studies show an association, others have found no link between injury and Alzheimer's risk. Much of the problem could be the fact that participants in other studies have been patients still alive when a definitive diagnosis of AD is not fully possible. Different criteria for what constitutes dementia is also a factor, and the result is that data in other studies might have included patients who did not have AD.
While the study is significant because it gives researchers a direction in which to go for future clinical trials, they still don't know exactly what about a TBI could cause a link to Alzheimer's. Factors that might be involved are what the team hopes to tackle next. TBIs usually cause inflammation, and this could trigger a process in the brain that results in the beta-amyloid plaques developing and damaging neurons. Genetics could be at play, as well as triggers from other illnesses or stress.
The issue is complicated by the fact that in some studies, in-depth health history concerning head injuries isn't included. Also, there is no tracking of head injuries like there is with other illnesses or injuries. Youths that play a sport might have a mild concussion that gets missed but could still be a risk factor later in life. Dr. Collum and colleagues from the O'Donnell Brain Institute at UT are also working on other studies that investigate the connection between brain injury and conditions like depression and anxiety. The NCAA, the nation's governing board of college athletics, has also begun collecting data and tracking the health of close to 32,000 college players, but that data is a long-term effort. For now, it's only a correlation between TBI and dementia, but future work could uncover a definite link.