Ask the Expert: Can Concussion Cause Dementia? | Alzheimer's Prevention Registry

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August 16, 2017

Ask the Expert: Can Concussion Cause Dementia?

By Alzheimer's Prevention Registry

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This month’s expert is Robert Stern, PhD, Director of Clinical Research for the Chronic Traumatic Encephalopathy (CTE) Center and Director of the Alzheimer’s Disease Center Clinical Core, both at Boston University. 

Dear Dr. Stern,

My 75-year-old mother was doing well living on her own until she fell and hit her head. At the hospital emergency room we learned she had a mild concussion. But since she’s been home, Mom hasn’t been the same. I have been spending more time with her and notice that she’s more forgetful and takes a long time to answer simple questions. Could the concussion have brought on dementia?



Dear Robin,

The scenario you describe is one I hear frequently: An older individual who has lived independently experiences what appears to be a sharp decline in cognitive abilities after a fall that results in a concussion.

First, if you haven’t done so, I encourage you to schedule your mother for a physical exam that includes cognitive screening. Ask the medical team to explore all potential reasons for your mother’s cognitive decline – vitamin B-12 deficiency, hypothyroidism and clinical depression should be investigated. Also, share information about your mother’s recent mild traumatic brain injury (mTBI). It is important information for the team to have and will help them decide if additional tests are needed. They will then be able to advise you on your mother’s health.

Now to your question: Can a concussion trigger dementia? Research does not show that a single concussion – also known as mTBI – can cause dementia. In my experience, an older individual in the situation you describe could have undiagnosed dementia due to Alzheimer’s. Because it can progress slowly, Alzheimer’s disease may not be apparent until an event like this causes loved ones to increase monitoring of the person and perhaps share information among family members.

While concussions do not cause dementia due to Alzheimer’s, it’s possible a concussion could change the threshold of a condition that is already in progress. That is, someone may have an underlying neurodegenerative disease, like Alzheimer’s, but they have a high threshold for the manifestation of the memory and other cognitive symptoms. The new injury may disrupt the brain functioning such that there is a decrease in that threshold and the problems begin.

Robin, I hope you find the source of your mother’s recent health issues. As with any medical condition, once you have a diagnosis you can move forward with a plan.