As I noted before (click!), plenty of news outlets are willing to attribute Muhammad Ali’s Parkinson’s disease to the innumerable hits to the head that Ali received during his boxing career. It certainly seems to make sense, especially with all the recent news about football players developing CTE as a result of concussions they endured on the playing field (click!).
However, a recent FoxFeed blog gives what I sense is a more nuanced explanation of the relationship between head trauma and the onset of PD. I can’t really improve on this article, so I suggest you just click on it now, because it’s so smart and well-written.
However, here are a few excerpts that especially stand out:
Many have wondered whether repeated hits to the head caused [Muhammad Ali’s] PD. While it’s true that environmental factors — including head injury — have been associated with an increased risk of Parkinson’s, few (if any) have been determined to be definitive causes of the disease. Environmental factors and genetics may interact to cause disease, and this complex interplay makes it virtually impossible to point to the exact cause(s) in any individual.
And:
A number of genetic mutations are associated with Parkinson’s disease — some simply increase risk for the disease and others appear to be more direct causes. Many environmental factors (e.g., head trauma, pesticides and solvents) are also linked to an elevated risk of Parkinson’s. Generally though, these environmental risks are designated as “associations” rather than “causes” (i.e., for some reason they contribute to an increased risk but they are not sufficient to cause PD in and of themselves).
And (bolding mine):
To summarize, head trauma and traumatic brain injury are associated with an increased risk of Parkinson’s but the mechanisms for how they are connected are unclear and direct causation (head or brain injury actually causing Parkinson’s) has not been established. More work is necessary to fully understand this relationship.
I think it’s interesting that the more we know about PD, the less clear are the obvious explanations for what causes it. It’s kind of a paradox that often occurs in life: the more we study something, the murkier it gets. And even the word “we” is murky: do I mean the general public? Or the leading researchers?
If you’re reading this post right after I press the “publish” button, then come back in a few days, you’ll notice that I’ve probably changed some of the text as I thought about it more. That’s because I’ve continued to mull the issues over, arriving at new realizations.
