Association of environmental tobacco smoke with dementia and Alzheimer's disease among never smokers

Background: Environmental tobacco smoke (ETS) is known to be harmful; however, its association with dementia remains controversial and with Alzheimer's disease (AD) is unknown. Methods: Using a standard interview method, the author carried out a multicenter cross-sectional study of dementia in China by examining 2692 never-smoking people aged >= 60 years. Relative risks (RRs) of AD and all dementia, as diagnosed by psychiatrists, in relation to ETS were calculated in a multivariate regression model. Results: The adjusted RR for all dementia was 1.78 (95% confidence interval [CI]: 1.18-2.68). The increased risk was mainly from exposure to ETS at home (1.87, 95% CI: 1.19-2.93), and it was associated with exposure duration. The adjusted RR for AD was 2.28 (95% CI: 1.82-2.84); the matched figure for ETS exposure at home, at work, and at other places was 2.15 (95% CI: 1.69-2.74), 2.04 (95% CI: 1.72-2.42), and 1.80 (95% CI: 0.96-3.38), respectively. The association of the increased risk with a total cumulative exposure dose was at borderline significance. Conclusions: The risk of dementia and AD increased with ETS exposure. Banning smoking in public areas may help reduce a dementia epidemic worldwide. (C) 2012 The Alzheimer's Association. All rights reserved.