[Workaccount2]

I'd encourage you to just search google scholar for "nicotine and parkinsons" there are dozens and dozens of studies. It's been well established for decades now, as it stood out, especially in the past, that cigarette smokers weren't developing parkinsons as expected. Here is a recent meta study though:

https://www.sciencedirect.com/science/article/abs/pii/S01674...

There have also been numerous studies that have found that starting nicotine once symptoms begin is too late, with little or no effect. It is hypothesized that there is some critical point that once crossed, nicotine no longer has an effect. Parkinsons is believed to slowly develop over years or decades, and nicotine stunts this early progression.