Secondhand smoke exposure can lead to dementia through the same mechanisms that exposure contributes to coronary heart disease and stroke. Evidence suggests that secondhand smoke contributes to an increased risk of atherosclerosis1 and preliminary studies indicate a link between secondhand smoke exposure and dementia or cognitive decline,2 particularly among those with symptoms of cardiovascular disease.3, 4 Other mechanisms by which tobacco smoke may cause dementia include increasing plasma homocysteine, an independent risk factor for stroke, cognitive impairment and dementia, and oxidative stress leading to neural death.5 Further research is needed to confirm an association between dementia and secondhand smoke.
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1. US Department of Health and Human Services. The health consequences of involuntary exposure to tobacco smoke: A report of the Surgeon General. Atlanta, Georgia: US Department of Health and Human Services, Centers for Disease Control and Prevention, Coordinating Center for Health Promotion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2006. Available from: http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2006/index.htm
2. Ling J and Heffernan T. The cognitive deficits associated with second-hand smoking. Frontiers in Psychiatry, 2016; 7:46. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27047401
3. Barnes D, Haight T, Mehta K, Carlson M, Kuller L, et al. Secondhand smoke, vascular disease, and dementia incidence: Findings from the cardiovascular health cognition study. American Journal of Epidemiology, 2010; 171(3):292–302. Available from: http://aje.oxfordjournals.org/cgi/content/full/171/3/292
4. Llewellyn D, Lang I, Langa K, Naughton F, and Matthews F. Exposure to secondhand smoke and cognitive impairment in non-smokers: National cross sectional study with cotinine measurement. British Medical Journal, 2009; 338:b462. Available from: http://www.bmj.com/cgi/content/full/338/feb12_2/b462?view=long&pmid=19213767
5. McKenzie J, Bhatti L, and d'Espaignet T. Tobacco and dementia. WHO Tobacco Knowledge Summaries, Geneva: World Health Organisation, 2014. Available from: http://apps.who.int/iris/bitstream/10665/128041/1/WHO_NMH_PND_CIC_TKS_14.1_eng.pdf