SMOKING AND ALZHEIMERS-DISEASE - A REVIEW OF THE EPIDEMIOLOGIC EVIDENCE

Overall evidence from 19 case-control studies of Alzheimer's disease ( AD) and smoking shows a highly significant (p < 0.001) negative associ ation [ever/never smokers, relative risk (RR) 0.64, 95% confidence int erval (CI) 0.54-0.76]. Some studies have apparent design faults but th e association is clearly evident in those which do not (RR 0.60, 95% C I 0.46-0.78). A report of a positive relationship from a prospective s tudy can be dismissed due to unreliability of AD diagnosis on death ce rtificates, and other study weaknesses. Although more data are needed on dose response and to rule out possible confounding, the negative as sociation is consistent with other data suggesting nicotine protects a gainst AD.