title: Cigarette smoking is a risk factor for Alzheimer's Disease: an analysis controlling for tobacco industry affiliation.
abstract: To examine the relationship between smoking and Alzheimer's disease (AD) after controlling for study design, quality, secular trend, and tobacco industry affiliation of the authors, electronic databases were searched; 43 individual studies met the inclusion criteria. For evidence of tobacco industry affiliation, http://legacy.library.ucsf.edu was searched. One fourth (11/43) of individual studies had tobacco-affiliated authors. Using random effects meta-analysis, 18 case control studies without tobacco industry affiliation yielded a non-significant pooled odds ratio of 0.91 (95% CI, 0.75-1.10), while 8 case control studies with tobacco industry affiliation yielded a significant pooled odds ratio of 0.86 (95% CI, 0.75-0.98) suggesting that smoking protects against AD. In contrast, 14 cohort studies without tobacco-industry affiliation yielded a significantly increased relative risk of AD of 1.45 (95% CI, 1.16-1.80) associated with smoking and the three cohort studies with tobacco industry affiliation yielded a non-significant pooled relative risk of 0.60 (95% CI 0.27-1.32). A multiple regression analysis showed that case-control studies tended to yield lower average risk estimates than cohort studies (by -0.27 +/- 0.15, P=0.075), lower risk estimates for studies done by authors affiliated with the tobacco industry (by -0.37 +/- 0.13, P=0.008), no effect of the quality of the journal in which the study was published (measured by impact factor, P=0.828), and increasing secular trend in risk estimates (0.031/year +/- 0.013, P=0.02). The average risk of AD for cohort studies without tobacco industry affiliation of average quality published in 2007 was estimated to be 1.72 +/- 0.19 (P< 0.0005). The available data indicate that smoking is a significant risk factor for AD.
authors.affiliation: Department of Physiological Nursing, Gerontology, University of California, San Francisco, San Francisco, CA 94143-0610, USA. cataldo@nursing.ucsf.edu
authors.forename: Janine K
authors.initials: JK
authors.lastname: Cataldo
authors.forename: Judith J
authors.initials: JJ
authors.lastname: Prochaska
authors.forename: Stanton A
authors.initials: SA
authors.lastname: Glantz
mesh_terms: D000544:Alzheimer Disease / Q000453:epidemiology* / Q000209:etiology*; D016022:Case-Control Studies; D016001:Confidence Intervals; D016265:Conflict of Interest; D057286:Electronic Health Records / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D015201:Meta-Analysis as Topic; D016017:Odds Ratio; D012044:Regression Analysis; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D014028:Tobacco Smoke Pollution