Using data from a large online survey sponsored by the Michael J. Fox Foundation for Parkinson’s Research, researchers found that participants who had a history of playing organized tackle football were 61% more likely to report a Parkinson’s disease diagnosis or parkinsonism, an umbrella term for symptoms like tremors and rigidity that cause movement problems, compared with those who played other organized sports.
There’s some genetic aspect but it doesn’t seem to run in families like a real genetic disease, so it’s probably a result of damage (physical trauma and/or toxins) and the genetic component is just a predisposition.