Exposure to second-hand smoke boosts the risk of dementia and other cognitive problems, even among people who have never smoked, the largest study of its kind reported Friday.  Ill effects on non-smokers of constant exposure to tobacco smoke include an increased risk of lung cancer, diabetes, cardiovascular disease, stroke and death, earlier research has shown.  Using new methods in the largest clinical trial to date, a team led by Cambridge University professor David Llewellyn found that even people who had never smoked but kept constant company with smokers performed less well in cognitive tests.  If smoking is already this bad for you when it's just passively inhaled, then think how bad it is for a person to be completely addicted to chain smoking.  I never thought it could hurt me having a cigarette here and there on the weekends, but I'm definitely going to stop now. 

That's so good you made that decision to quit...  Dementia is nothing to wish on anybody, and the passive smoking is certainly not worth this risk.  Good job, I hope more people can read this and make similar good decisions.