The influence of smoking on the risk of Alzheimer's disease

Objective: To investigate the relationship between cigarette smoking and Al zheimer's disease(AD) in a prospective community-based study in northern Ma nhattan. Background: Results from previous case-control studies suggest tha t there is a protective effect of smoking on AD. However, the recent prospe ctive Rotterdam Study found that there was an increased risk of AD far smok ers, particularly those without an apolipoprotein E (APOE)-epsilon 4 allele . Methods: The authors examined data from a community-based longitudinal st udy of local elders residing in northern Manhattan to determine whether tob acco use increases or decreases the risk of AD. Information regarding the f requency of tobacco use was obtained in structured interviews at the baseli ne assessment. Standardized clinical assessments were subsequently complete d on each subject at annual visits during which incident cases of AD were i dentified. Results: The relative risk (RR) of AD among former smokers was 0 .7 (95% CI, 0.5 to 1.1). The RR among current smokers was 1.9 (95% CI, 1.2 to 3.0). Smokers without an APOE-epsilon 4 allele had the highest risk of A D (RR = 2.1; 95% CI, 2.1 to 3.7) compared with those with an APOE-epsilon 4 allele (RR = 1.4; 95% CI, 0.6 to 3.3). Conclusions: Our results are consis tent; with the observation that smoking increases the risk of AD, However,w e found that among previous smokers who quit smoking, there may be a slight reduction in the risk. of AD.