Large Study Finds Head Knocks Are Not Associated with Alzheimer's Disease
Do head knocks eventually lead to Alzheimer’s disease? Many studies have reported this link, but a new large study has unexpectedly found the opposite. Michael Weiner, MD, professor in residence in the UC San Francisco Department of Radiology and Biomedical Imaging and the San Francisco Veterans Affairs Medical Center (SFVAMC) set out to examine the question in Vietnam veterans.
His study, reported in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, had one key difference - how Alzheimer’s disease was defined. While in previous studies Alzheimer’s disease has been diagnosed by a physician using tests of cognition and function, in this study, researchers used biological indicators of Alzheimer’s disease.
These so-called biomarkers reflect the hallmark lesions associated with the disease - β-amyloid plaques and tau fibrils - along with showing brain shrinkage. After extensive screening of more than 26,000 Vietnam veterans identified from medical records, the study enrolled 289 participants. They underwent tests for Alzheimer’s disease biomarkers as well as cognitive assessments and scans for blood vessel damage that can also lead to cognitive problems.
“The study found that, as expected, more of the veterans who had suffered concussions were clinically diagnosed mild cognitive impairment (which often leads to dementia), and fared worse on a particular cognitive test,” says Dr. Weiner, who is also the principal investigator of the Alzheimer's Disease Neuroimaging Initiative (ADNI), which is the largest observational study in the world concerning Alzheimer's disease and the UCSF Brain Health Registry (BHR).
However, contrary to Dr. Weiner’s expectations, there was no difference between groups in Alzheimer’s disease biomarkers or brain blood vessel damage, either at one time point or over several years. In other words, even though these head knocks were associated with more mild cognitive impairment, they were not associated with biomarkers of amyloid, tau or neurodegeneration which are the hallmarks of Alzheimer’s disease.
These findings emphasize the point that the clinical diagnosis of mild cognitive impairment or dementia cannot accurately determine the underlying cause of the problem. Cognitive impairments and dementia can be caused by multiple factors in addition to Alzheimer’s disease pathology.
“This study will be encouraging news for veterans, and others, who have suffered from concussions or head knocks – the diagnosis of Alzheimer’s disease should not be in the future as a result of these injuries,” says Dr. Weiner.
Duygu Tosun-Turgut, PhD, associate professor at UCSF Radiology, was a collaborator on this study, along with investigators from UC Davis, UC Berkeley, UC San Diego, SFVAMC, UCSF Neurology, Indiana University School of Medicine, Northwestern University School of Medicine and the University of Pennsylvania School of Medicine.