Alzheimer's Disease Education and Referral Center

Study shows possible link between secondhand smoke, cognitive impairment

May 12, 2009

A recent article about a population-based study in England reports that exposure to secondhand smoke could increase the odds of older nonsmokers becoming cognitively impaired.

In work funded in part by the NIA, researchers measured levels of salivary cotinine, a nicotine metabolite that indicates exposure to secondhand smoke, in 4,809 adults ages 50 and older. All participants were nonsmokers who did not use nicotine products but were exposed to smoking—at home, in the workplace, or in other locations. The sample was drawn from the multiyear Health Survey for England and the 2002 wave of the English Longitudinal Study of Ageing.

Individuals with the highest concentrations of cotinine—and thus more exposure to secondhand smoke—were more likely than those with lower concentrations to become cognitively impaired, as measured by their performance on neuropsychological tests. Dr. David J. Llewellyn of the University of Cambridge and colleagues found that these results held after controlling for risk factors for cognitive decline, including age, education, and the presence of cardiovascular disease. Perhaps surprisingly, there was even a trend toward stronger cognitive impairment in those who had never smoked.

The authors note that the results are consistent with previous findings that active smoking may raise the risk of cognitive impairment, but further research is needed to establish if and how secondhand smoke might cause cognitive decline.


Llewellyn DJ, et al. Exposure to secondhand smoke and cognitive impairment in non-smokers: national cross sectional study with cotinine measurement. BMJ. 2009 Feb 12. 338:b462.

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