Traumatic brain injury and Parkinson’s disease – an association


A new study has found traumatic brain injury with loss of consciousness is associated with the risk of Parkinson’s disease, but (interestingly) not Alzheimer’s disease. In this post we will review the study and its findings, before considering the implications of the results.


Image sourced from GQ

There has been a lot of talk on the interweb and various media outlets recently about the long term consequences of head injuries associated with physical sports like boxing, rugby, ice hockey and American football (click here for more on this).

Of particular concern is when individuals lose consciousness at the time of the head injury, which has been associated with worse outcomes than simply suffering a bang on the head.

A group of American researchers recently decided to assess whether there was any association between traumatic head injury with loss of consciousness and the increased risk for Alzheimer’s disease.

What they found may have profound implications for Parkinson’s disease.


Title: Association of Traumatic Brain Injury With Late-Life Neurodegenerative Conditions and Neuropathologic Findings.
Authors: Crane PK, Gibbons LE, Dams-O’Connor K, Trittschuh E, Leverenz JB, Keene CD, Sonnen J, Montine TJ, Bennett DA, Leurgans S, Schneider JA, Larson EB.
Journal: JAMA Neurol. 2016 Jul 11. doi: 10.1001/jamaneurol.2016.1948.
PMID: 27400367       (This study is OPEN ACCESS if you would like to read it)

The researchers collected the results of 3 large studies, collectively involving 7130 participants who had head injury data (2879 men and 4251 women; average age of 79.9 years). Of these 845 had suffered traumatic brain injuries with loss of consciousness for at least 1 hour. Interestingly, the researchers found no statistically significant association between traumatic brain injuries with loss of consciousness and risk of Alzheimer’s disease.

Next they looked at Parkinson’s disease and found that people who suffered traumatic brain injuries with loss of consciousness of more than 1 hour had a statistically significant increase in developing Parkinson’s disease (2-3 times more than normal controls).

Of the 7130 participants in the study, postmortem autopsy analysis reports were available for 1589 of the subjects. The researchers looked for the neuropathological hallmarks of Parkinson’s disease, called Lewy bodies, and they found no correlation between people who suffered traumatic brain injuries with loss of consciousness of less than 1 hour and the presence of Lewy bodies. When they looked in the brains of people who suffered traumatic brain injuries with loss of consciousness of more than 1 hour, they did find a correlation. And importantly these neuropathological events were not associated with genetic mutations.

So what does it all mean? 


The results indicate that traumatic brain injuries with loss of consciousness of more than 1 hour could significantly increase a person’s risk of Parkinson’s disease. The crucial  detail in the results is the ‘loss of consciousness of more than 1 hour’. Traumatic head injury can often result in disruption to the blood-brain-barrier (the protective film surrounding the brain), which may result in certain pathogens entering the brain. So the more severe the injury, perhaps the longer the barrier is disrupted. Why this event may relate solely to Parkinson’s disease and not Alzheimer’s disease, however, remains to be determined.

It would be interesting to assess how this finding relates to the greater Parkinson’s community. That is to say, determine how many of the people with Parkinson’s disease have a head injury with loss of consciousness in their past medical records?

Reading this study, one cannot help thinking of the recent passing of Boxing great Muhammad Ali. Ali died this year having spent the last third of his life living with Parkinson’s disease. Many boxing careers have probably involved one or two severe head injuries with loss of consciousness, so why are there not more cases of Parkinson’s disease in the boxing community? Many retired boxers suffer from what is called Dementia pugilistica – a neurodegenerative condition with Alzheimer’s-like dementia. Some estimates suggest that 15-20% of boxers may be affected, with symptoms usually starting 12-16 years after the start of a career in boxing. Some very famous boxers have been diagnosed with this condition, including world champions Floyd Patterson, Joe Louis, Sugar Ray Robinson and boxer/coach Freddie Roach.

The difference between the results of today’s study and dementia pugilistica may lie in the repeated nature of the injuries in boxers and the length of time individuals were unconscious. It will be interesting to see what becomes of this research.



The banner for today’s post was sourced from the Huffington Post

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