The Grapevine

A Single Mild Concussion Can Increase Risk Of Parkinson's Disease: Study

In a large study of United States veterans, researchers from the University of California, San Francisco, were able to find a link between traumatic brain injury (TBI) and the risk of Parkinson's disease. Mild TBIs, commonly known as concussions, were also examined. The results showed even people who were diagnosed with a mild concussion faced a 56 percent increased risk of developing Parkinson's.

"While our study looked at veterans, we believe the results may have important implications for athletes and the general public as well," said lead author Dr. Raquel Gardner, an assistant professor of neurology.

The paper titled “Mild TBI and risk of Parkinson disease” was published in the medical journal Neurology on April 18.

"Our research looked a very large population of U.S. veterans who had experienced either mild, moderate or severe traumatic brain injury in an effort to find an answer to whether a mild traumatic brain injury can put someone at risk," said senior study author Dr. Kristine Yaffe, a professor of psychiatry, neurology, and epidemiology.

The researchers highlighted the importance of the findings for two reasons. First, the study looked at every single veteran who had been diagnosed at a Veterans Affairs hospital, providing the highest level of evidence to date. Secondly, while previous research linked TBI with the risk of Parkinson's, studies on its mild form have not been conclusive.

For the study, 325,870 veterans — ranging from 31 to 65 years of age — were recruited from three U.S. Veterans Health Administration medical databases and followed from 2002 to 2014. At the start of the study, none of them had Parkinson's disease or dementia. Initially, roughly 50 percent of the participants were diagnosed with mild, moderate or severe TBI, while the other half was not. 

Among the participants, 1,462 were eventually diagnosed with Parkinson's at some point during the 12-year study. Of those, 949 participants had previously suffered a concussion. While those with mild TBI had a 56 percent increased risk of developing Parkinson's, those with moderate to severe condition faced an 83 percent increase in risk.

"This study highlights the importance of concussion prevention, long-term follow-up of those with concussion, and the need for future studies to investigate if there are other risk factors for Parkinson's disease that can be modified after someone has a concussion," said Dr. Gardner.

In the study, a moderate to severe TBI was defined as a loss of consciousness for more than 30 minutes, alteration of consciousness of more than 24 hours or amnesia for more than 24 hours. A mild TBI was defined as a loss of consciousness for zero to 30 minutes, alteration of consciousness of a moment to 24 hours or amnesia for zero to 24 hours.

Parkinson's disease is considered to be rare, especially for people under the age of 40. Some of the early signs to watch out for include a resting hand tremor, changes in facial expressions and handwriting, reduced sense of smell, a softer voice, etc.