3.23 Smoking, dementia and cognitive decline

Last updated: April 2015
Suggested citation: Letcher, T, Greenhalgh, EM & Winstanley, MH. 3.23 Smoking, dementia and cognitive decline. In Scollo, MM and Winstanley, MH [editors]. Tobacco in Australia: Facts and issues. Melbourne: Cancer Council Victoria; 2015. Available from http://www.tobaccoinaustralia.org.au/3-23-smoking-dementia-and-cognitive-decline

 

Several systematic reviews have concluded that there is a likely association between current smoking and an increased risk of incident dementia, especially Alzheimer's disease, and that smoking may be a risk factor for cognitive decline.1,2,3

A review of comparable research published up to June 2005 concluded that older smokers may have a greater risk of developing dementia (including Alzheimer's disease and vascular dementia) and cognitive decline than non-smokers.1 This meta-analysis focused on those over the age of 65 years, and included only longitudinal studies. It showed that current smokers had a 40–80% increased likelihood of experiencing dementia and cognitive decline compared with never smokers. The authors of this review observed that individual lifestyle and physiological factors may also influence the association between smoking, dementia and cognitive decline, and that further research is needed.1

A similar systematic review based on longitudinal studies published between 1995 and 2007 examined the relationship between smoking, dementia and cognitive decline in an elderly population (aged 65 years and over).2 Meta-analyses found current smokers compared with never or non-smokers had a significantly increased risk of Alzheimer's disease and a higher but not significantly increased risk of cognitive decline, vascular and unspecified dementia.2 Contrary to the findings of a number of early studies suggesting that smoking may be protective against Alzheimer's disease,4-9 a systematic review of all research published up to 2007 concluded that current or ever smoking is in fact a significant risk factor for Alzheimer's disease.3 The review controlled for study design, quality, secular trend and tobacco industry affiliation of study authors. One-quarter of the 43 studies reviewed had tobacco-affiliated authors. Based on average quality cohort studies with no tobacco industry affiliation published in 2007, the average risk of Alzheimer's disease associated with smoking was estimated to be 1.72 +/– 0.19 (p<0.0005).3

A review of the peer-reviewed literature on the neurocognitive and neurobiological implications of chronic smoking (not defined specifically) concluded there is increasing evidence that chronic cigarette smoking is associated with demonstrable abnormalities in brain neurobiology and neurocognition across the lifespan, and is related to abnormal rates of loss of brain volume in the elderly.10 Focusing on smoking among cohorts and population-based samples not seeking treatment for substance use or psychiatric disorders, the authors found a likely association between chronic smoking and diminished executive functions, cognitive flexibility, general intellectual abilities, learning and/or memory processing speed, and working memory.10

Several prospective cohort studies not included in the above reviews have also examined the effect of smoking in middle age on cognitive decline and dementia.11,12,13 This is partly to address the selection bias caused by differential mortality among smokers when examining the effects of smoking among the elderly:13 middle-aged smokers are more likely to be lost to follow-up by death or through non-participation in cognitive tests.14 These studies provide further evidence of associations between smoking and dementia,11,12 Alzheimer's disease,12 vascular dementia, loss of cognitive flexibility and global cognitive function.13

Most recently, Alzheimer’s Disease International conducted a large-scale review of the association between lifestyles and dementia risk, and reported robust evidence for a relationship between current smoking (vs. never smoking) and the incidence of Alzheimer’s disease. Evidence also suggested (though the relationship was non-statistically significant) a similar association with vascular dementia, and a smaller association with any dementia. Conversely, ex-smokers were at a similar risk to those who have never smoked for all types of incident dementia. These findings are important for prevention and cessation efforts, as the increased risk of dementia might be avoided by quitting smoking.15

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References

1. Anstey K, von Sanden C, Salim A and O'Kearney R. Smoking as a risk factor for dementia and cognitive decline: a meta-analysis of prospective studies. American Journal of Epidemiology 2007;166(4):367–78. Available from: http://aje.oxfordjournals.org/cgi/reprint/166/4/367

2. Peters R, Poulter R, Warner J, Beckett N, Burch L and Bulpitt C. Smoking, dementia and cognitive decline in the elderly, a systematic review. BMC Geriatrics 2008;8(1):36. Available from: http://www.biomedcentral.com/content/pdf/1471-2318-8-36.pdf

3. Cataldo J, Prochaska J and Glantz S. Cigarette smoking is a risk factor for Alzheimer's disease: an analysis controlling for tobacco industry affiliation. Journal of Alzheimer's Disease 2010;19(2):465–80. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20110594

4. Fratiglioni L and Wang H. Smoking and Parkinson's and Alzheimer's disease: review of the epidemiological studies. Behavioral Brain Research 2000;113(1-2):117-20. Available from: http://www.ncbi.nlm.nih.gov/pubmed/10942038

5. Graves A, van Duijn C, Chandra V, Fratiglioni L, Heyman A, Jorm A, et al. Alcohol and tobacco consumption as risk factors for Alzheimer's disease: a collaborative re-analysis of case-control studies. EURODEM Risk Factors Research Group. International Journal of Epidemiology 1991;20(suppl. 2):S48-S57. Available from: http://www.ncbi.nlm.nih.gov/pubmed/1833354

6. Lee P. Smoking and Alzheimer's disease: a review of the epidemiological evidence. Neuroepidemiology 1994;13(4):133-44. Available from: http://www.ncbi.nlm.nih.gov/pubmed/8090255

7. Smith C and Giacobini E. Nicotine, Parkinson's and Alzheimer's disease. Reviews in the Neurosciences 1991;3(1):25-43. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21561277

8. van Duijn C, Clayton D, Chandra V, Fratiglioni L, Graves A, Heyman A, et al. Interaction between genetic and environmental risk factors for Alzheimer's disease: a reanalysis of case-control studies. EURODEM Risk Factors Research Group. Genetic Epidemiology 1994;11(6):539-51. Available from: http://www.ncbi.nlm.nih.gov/pubmed/7713394

9. Chen G, Payne T, Lou X, Ma J, Zhu J and Li M. Association of amyloid precursor protein-binding protein, family B, member 1 with nicotine dependence in African and European American smokers. Human Genetics 2008;124(4):393-8. Available from: http://www.ncbi.nlm.nih.gov/pubmed/18777128

10. Durazzo TC, Meyerhoff DJ and Nixon SJ. Chronic cigarette smoking: implications for neurocognition and brain neurobiology. International Journal of Environmental Research and Public Health 2010;7(10):3760–91. Available from: http://www.mdpi.com/1660-4601/7/10/3760/pdf

11. Alonso A, Mosley T Jr, Gottesman R, Catellier D, Sharrett A and Coresh J. Risk of dementia hospitalisation associated with cardiovascular risk factors in midlife and older age: the Atherosclerosis Risk in Communities (ARIC) study. Journal of Neurology, Neurosurgery & Psychiatry 2009;80(11):1194-201. Available from: http://jnnp.bmj.com/content/80/11.toc

12. Rusanen M, Kivipelto M, Quesenberry C, Jr, Zhou J and Whitmer R. Heavy smoking in midlife and long-term risk of Alzheimer disease and vascular dementia. Archives of Internal Medicine 2011;171(4):333–9. Available from: http://archinte.ama-assn.org/cgi/content/full/171/4/333

13. Nooyens AC, van Gelder BM and Verschuren WM. Smoking and cognitive decline among middle-aged men and women: the Doetinchem cohort study American Journal of Public Health 2008;98(12):2244-50. Available from: http://www.ajph.org/cgi/reprint/AJPH.2007.130294v1

14. Sabia S, Marmot M, Dufouil C and Singh-Manoux A. Smoking history and cognitive function in middle age from the Whitehall II Study Archives of Internal Medicine 2008;168(11):1165–73. Available from: http://archinte.ama-assn.org/cgi/content/full/168/11/1165

15. Alzheimer's Disease International. World Alzheimer Report 2014. London, UK 2014. Available from: http://www.alz.co.uk/research/WorldAlzheimerReport2014.pdf

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