Smoking as a Risk Factor for Dementia and Cognitive Decline: A Meta-Analysis of Prospective Studies

• Published in: American journal of epidemiology 2007-08, Vol.166 (4), p.367-378
• Main Authors: Anstey, Kaarin J., von Sanden, Chwee, Salim, Agus, O'Kearney, Richard
• Format: Article
• Language: English
• Subjects: Aged; Alzheimer disease; Alzheimer's disease; Analysis. Health state; Biological and medical sciences; cognition; Cognition & reasoning; Cognition Disorders - epidemiology; Cognition Disorders - etiology; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Dementia; Dementia - epidemiology; Dementia - etiology; Epidemiology; Female; Follow-Up Studies; General aspects; Humans; Incidence; Male; Medical sciences; Meta-analysis; Neurology; Prospective Studies; Public health. Hygiene; Public health. Hygiene-occupational medicine; Risk Factors; Smoking; Smoking - adverse effects; Tobacco, tobacco smoking; Toxicology; vascular
• ISSN: 0002-9262; 1476-6256
• DOI: 10.1093/aje/kwm116

The authors assessed the association of smoking with dementia and cognitive decline in a meta-analysis of 19 prospective studies with at least 12 months of follow-up. Studies included a total of 26,374 participants followed for dementia for 2–30 years and 17,023 participants followed up for 2–7 years to assess cognitive decline. Mean study age was 74 years. Current smokers at baseline, relative to never smokers, had risks of 1.79 (95% confidence interval (CI): 1.43, 2.23) for incident Alzheimer's disease, 1.78 (95% CI: 1.28, 2.47) for incident vascular dementia, and 1.27 (95% CI: 1.02, 1.60) for any dementia. Compared with those who never smoked, current smokers at baseline also showed greater yearly declines in Mini-Mental State Examination scores over the follow-up period (effect size (β) = −0.13, 95% CI: −0.18, −0.08). Compared with former smokers, current smokers at baseline showed an increased risk of Alzheimer's disease (relative risk = 1.70, 95% CI: 1.25, 2.31) and an increased decline in cognitive abilities (effect size (β) = −0.07, 95% CI: −0.11, −0.03), but the groups were not different regarding risk of vascular dementia or any dementia. The authors concluded that elderly smokers have increased risks of dementia and cognitive decline.