> This puzzled me, as these Alzeheimer's and smoking results do not seem to be evidence of evolution; one would surely need to see a decrease over generations?

At least with smoking, we've been experiencing exactly that decrease for generations. Smoking has become vastly unpopular compared to how prevalent and socially accepted it used to be. Social factors had been one of the main driving forces, but that doesn't mean it has to be the only driving force.