Secondhand smoke exposure may 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 atherosclerosis.1 Other mechanisms by which tobacco smoke may cause dementia include increasing plasma homocysteine levels, an independent risk factor for stroke, cognitive impairment and dementia, and oxidative stress leading to neural death.2 A number of studies indicate an association between secondhand smoke exposure and dementia or cognitive decline,3-6 particularly among those with symptoms of cardiovascular disease.7, 8 A systematic review of observational studies found eight papers showing a weak association between passive smoking and either cognitive impairment or dementia.9 The authors of this study concluded that there was limited weak observational evidence linking passive smoking with an increased risk of cognitive impairment or dementia. Further research is necessary to confirm this finding and ask whether exposure to secondhand smoke is causing these effects.
A study of over 20,000 students in China showed that showed that those exposed to secondhand smoke were more likely to have atopic dermatitis and hand eczema. This study also showed a dose-response of smoking on dermatitis and eczema, with the duration and amount of exposure.10
Non-smokers with past or current exposure to secondhand smoke had a higher chance of abnormal menstrual cycle compared to unexposed people in a study of almost 5,000 women in Japan.11
A 31-year prospective cohort study showed that secondhand smoke exposure was associated with increased risk of adult fatty liver disease in both children and adults.12
A meta-analysis found that people exposed to secondhand smoke had a higher chance of sleep disturbances, however higher quality studies are necessary to confirm this result.13
Relevant news and research
For recent news items and research on this topic, click here.(Last updated January 2021)
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. McKenzie J, Bhatti L, and d'Espaignet T. Tobacco and dementia. WHO Tobacco Knowledge Summaries, Geneva: WHO, 2014. Available from: http://apps.who.int/iris/bitstream/10665/128041/1/WHO_NMH_PND_CIC_TKS_14.1_eng.pdf.
3. Ling J and Heffernan T. The cognitive deficits associated with second-hand smoking. Frontiers in Psychiatry, 2016; 7:46. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27047401
4. Bai A, Jin Y, and Huang Y. Impact of secondhand smoke exposure on cognitive function among middle-aged and older women in China: findings from three waves of the China Health and Retirement Longitudinal Study. BMJ Open, 2020; 10(11):e039824. Available from: https://www.ncbi.nlm.nih.gov/pubmed/33203633
5. He F, Li T, Lin J, Li F, Zhai Y, et al. Passive smoking exposure in living environments reduces cognitive function: A prospective cohort study in older adults. International Journal of Environmental Research and Public Health, 2020; 17(4). Available from: https://www.ncbi.nlm.nih.gov/pubmed/32098188
6. Akhtar WZ, Andresen EM, Cannell MB, and Xu X. Association of blood cotinine level with cognitive and physical performance in non-smoking older adults. Environmental Research, 2013; 121:64-70. Available from: https://www.ncbi.nlm.nih.gov/pubmed/23199696
7. Barnes DE, Haight TJ, Mehta KM, Carlson MC, Kuller LH, 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: https://www.ncbi.nlm.nih.gov/pubmed/20051462
8. Llewellyn DJ, Lang IA, Langa KM, Naughton F, and Matthews FE. 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: https://www.ncbi.nlm.nih.gov/pubmed/19213767
9. Stirland LE, O'Shea CI, and Russ TC. Passive smoking as a risk factor for dementia and cognitive impairment: systematic review of observational studies. International Psychogeriatrics, 2018; 30(8):1177-87. Available from: https://www.ncbi.nlm.nih.gov/pubmed/29249209
10. Jing D, Li J, Tao J, Wang X, Shan S, et al. Associations of second-hand smoke exposure with hand eczema and atopic dermatitis among college students in China. Scientific Reports, 2020; 10(1):17400. Available from: https://www.ncbi.nlm.nih.gov/pubmed/33060809
11. Sakai H and Ohashi K. Effects of past environmental tobacco smoke exposure on the menstrual cycle and menstrual phase-related symptoms: A cross-sectional study. Journal of Obstetrics and Gynaecology Research, 2021; 47(1):243-53. Available from: https://www.ncbi.nlm.nih.gov/pubmed/33103300
12. Wu F, Pahkala K, Juonala M, Jaakkola J, Rovio SP, et al. Childhood and adulthood passive smoking and nonalcoholic fatty liver in midlife: A 31-year cohort study. The American Journal of Gastroenterology, 2021. Available from: https://www.ncbi.nlm.nih.gov/pubmed/33481379
13. Safa F, Chaiton M, Mahmud I, Ahmed S, and Chu A. The association between exposure to second-hand smoke and sleep disturbances: A systematic review and meta-analysis. Sleep Health, 2020; 6(5):702-14. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32446663