On page 6D of today's USA Today there is an excellent article about the connection between smoking and the risk of developing Alzheimers. The bottom line: Heavy smoking in midlife more than doubles your odds of developing Alzheimers disease.
You can read the article HERE.
I can think of far fewer worse way to go than to simply have your brain cells atrophy as you slide into a walking-dead like state. That's the kind of thing that makes even people faith question the notion of a loving God.
As I've noted here on many an occasion, please, if you smoke try and quit. If you can't quit, keep trying. I don't care if I know you or not, as no one deserves to deal with the very real health hazards that are caused by smoking. Come on people, this is simply not worth it.