On the flip side, there have been studies that indicate that nicotine may slow Alzheimers/dementia.
There's probably a study out there to back up and refute 98% of all diet-related issues - the trick is figuring out which, if any, are correct or if they may not be across-the-bard correct, but be valid for specific physiologies.
I have always wondered about the negative association between Parkinsons and apparently other neurological diseases and smoking cigarettes. Maybe the diseases are caused by parasites that are killed by the nicotine at some point in life.