Smoking history and Alzheimer's disease risk in a community-based clinic population

The relationship between cigarette smoking and development of Alzheimer's disease (AD) is not fully determined, and previous reports disagree, with some studies suggesting an increased relative risk and others a decreased odds ratio. Consequently, we wanted to determine if the prevalence of past cigarette smoking observed in a community-based clinic sample of patients with AD would be more consistent with the expected value obtained from a model using either an increased relative risk or a decreased odds ratio to estimate the effect of smoking on development of AD.

Retrospective cross-sectional analysis of all patients treated for AD in a community-based Neurology Clinic during a 2-year period. Estimates of expected past smoking prevalence were calculated based on published values for either an increased relative risk or a decreased odds ratio and compared to the past smoking prevalence observed in the clinic sample.

The observed past smoking prevalence in the clinic population was 29.17%. The expected past smoking prevalence calculated using the increased relative risk was 30.07% (95% confidence interval [CI] = 27.67-32.32%), and using the decreased odds ratio was 12.54% (95% CI = 6.32-24.81%).

The observed past smoking prevalence among the patients being treated for AD in a community-based clinic falls within the expected 95% CI for the increased relative risk model and outside of the expected 95% CI for the decreased odds ratio model. These results support the contention that the relationship between cigarette smoking and development of AD is the best characterized by an increased relative risk.