Association of passive smoking with cognitive impairment in nonsmoking older adults: a systematic literature review and a new study of Chinese cohort.

Association of passive smoking with cognitive impairment in older adults is unclear. We carried out a systematic literature review and a new study to determine the association. There were 3 cross-sectional studies published, showing a significant association of passive smoking with cognitive impairment (a relative risk (RR) of about 1.30-1.90). In the new cohort study, we interviewed 1081 never-smoking participants aged ≥ 65 years in China using a standard method of the Geriatric Mental State-Automated Geriatric Examination for Computer Assisted Taxonomy and found a significant association with dose response; multivariate adjusted RR was 1.02 (95% confidence interval 0.67-1.55) in > 0 to 49 exposure level years of passive smoking, 1.57 (1.00-2.47) in 50 to 99, and 2.12 (1.24-3.63) in ≥ 100, trend P = .008. The relationship seems not to be a reverse causality of the effect. Passive smoking could be considered an important risk factor for cognitive impairment in older adults. Avoiding exposure to passive smoking would help to preserve cognitive decline in later life.