Smokers have a 11-17% chance of developing lung cancer, according to this study.
1.) I'd rather have a 10% chance of dying than a 10% chance of living many years with something like Alzheimer's.
2.) I'm not someone who says "I wish I could quit but I'm addicted", I find it easy not to smoke but I do it because I really enjoy smoking. I'm trading possible early death with current pleasure. Alzheimer's doesn't have any upside or choice involved.
Probably should have added something like that to the original post, my pardon.