Smokers seem to have less bad symptoms too. The theory is that nicotine is protective, but it could be OTHER compounds in tobacco. Some people are trying nicotine patches just in case it helps.

We do know that nicotine helps people with Parkinson's disease.

I suspect it's other compounds in tobacco that are helpful. There is one, anatabine citrate, that is a powerful anti-inflammatory. No longer available as a dietary supplement, unfortunately.