Exposure to passive smoking and risk of dementia in older women who never smoke

Background: Exposure to passive smoking is linked to a number of known risk factors for dementia and has a negative effect on cognitive abilities. However, its direct association with dementia is uncertain and in women unknown. Methods: Using a standard interview method, we examined 2,386 never-smoking women aged ≥ 65 years in China. We characterised passive smoking exposure and diagnosed dementia using the 10/66 algorithm. Association of passive smoking exposure with dementia was calculated in a multivariate logistic regression model. Results: There were 33.0% of participants exposed to passive smoking and 150 dementia cases documented. Women exposed to passive smoking had a significantly increased risk of dementia (adjusted odds ratio (OR) was 1.44, 95% CI 1.00-2.05, p=0.048). The risk of dementia from passive smoking exposure at home was 1.53 (1.08-2.17), at work 2.65 (1.57-4.48) and in other places 1.95 (1.13-3.34). There were significant dose-response associations of exposure level and duration with dementia. The cumulative dose analysis showed an adjusted OR of 0.81 (0.38-1.74) for exposure at >0-39 level-years, 1.18 (0.66-2.11) at 40-79 level-years, 2.40 (1.79-3.23) at 80-119 level-years and 5.23 (2.51-10.9) at ≥ 120 level-years. Conclusions: Passive smoking could be considered an important risk factor for dementia in never-smoking women. Banning smoking in public areas may help reduce the growing dementia epidemic.