The association between secondhand smoke and cognition is biologically plausible. These results are consistent with evidence for an association between Alzheimer’s disease and "first-hand" smoking, and an association between particulate air pollution and cognitive decline, as reported in the same issue of the Archives of Internal Medicine (Weuve et al., 2012). However, these results are not consistent with a recent article on secondhand smoke and dementia (Barnes et al., 2010). Though the results of Chen et al. are interesting, the size of the effect in adjusted models is fairly weak, only being seen at the very highest exposure levels. I also have measurement concerns. They use a self-report of passive smoking, and an insufficient adjustment for cardiovascular disease—the association between secondhand smoke and dementia may be due to the association between cardiovascular disease and dementia rather than to secondhand smoke directly (see causal pathway in Barnes et al., 2010).

Also, the use of the Geriatric Mental Status (GMS) test and the Automated Geriatric Examination...  Read more

The association between secondhand smoke and cognition is biologically plausible. These results are consistent with evidence for an association between Alzheimer’s disease and "first-hand" smoking, and an association between particulate air pollution and cognitive decline, as reported in the same issue of the Archives of Internal Medicine (Weuve et al., 2012). However, these results are not consistent with a recent article on secondhand smoke and dementia (Barnes et al., 2010). Though the results of Chen et al. are interesting, the size of the effect in adjusted models is fairly weak, only being seen at the very highest exposure levels. I also have measurement concerns. They use a self-report of passive smoking, and an insufficient adjustment for cardiovascular disease—the association between secondhand smoke and dementia may be due to the association between cardiovascular disease and dementia rather than to secondhand smoke directly (see causal pathway in Barnes et al., 2010).

Also, the use of the Geriatric Mental Status (GMS) test and the Automated Geriatric Examination for Computer Assisted Taxonomy (AGECAT) algorithm to score it may be a problematic measurement of outcome (dementia diagnosis). According to Prince et al., 2004, "in developing countries, the GMS is a useful adjunct to diagnosis" but "the GMS on its own was never intended to provide a formal diagnosis of dementia. In developing countries and other low-education populations, the focus in the GMS/AGECAT algorithm upon educationally biased cognitive test items risks overdiagnosis. If the GMS is to be used alone in developing-country and other low-education populations, then caution is indicated in interpreting the organicity output, which may not map as closely onto clinical dementia as in a developed-country population.”

References:
Barnes DE, Haight TJ, Mehta KM, Carlson MC, Kuller LH, Tager IB. Secondhand smoke, vascular disease, and dementia incidence: findings from the cardiovascular health cognition study. Am J Epidemiol. 2010;171(3):292-302. Abstract

Prince M, Acosta D, Chiu H, et al; 10/66 Dementia Research Group. Effects of education and culture on the validity of the Geriatric Mental State and its AGECAT algorithm. Br J Psychiatry. 2004;185:429-436. Abstract

Weuve J, Puett RC, Schwartz J, Yanosky JD, Laden F, Grodstein F. Exposure to particulate air pollution and cognitive decline in older women. Arch Intern Med. 2012 Feb 13;172(3):219-27. Abstract

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