A Curtin University-led review of 61 prospective studies found that dementia risk estimates climbed with daily cigarette use, adding evidence on a potential brain-health cost of smoking while leaving causation unresolved.
The meta-analysis included about 2.8 million people. Compared with never smokers, its pooled dementia risk estimate was 16% higher for people who smoked 10 cigarettes a day and 34% higher for those smoking 20 a day. The estimates are relative comparisons and do not show an individual's absolute chance of dementia.
The dose-response analysis put those pooled relative risks at 1.16 (95% confidence interval, 1.09 to 1.23) and 1.34 (1.18 to 1.51), respectively. Across the review, current smokers also had risk estimates 31% higher for all-cause dementia, 40% higher for Alzheimer's disease and 52% higher for vascular dementia than never smokers.
The pooled estimates came from 39 studies for all-cause dementia, 19 for Alzheimer's disease and nine for vascular dementia. Their relative risks were 1.31 (95% confidence interval, 1.23 to 1.39), 1.40 (1.06 to 1.80) and 1.52 (1.20 to 1.93), respectively.
Compared with never smokers, former smokers showed no statistically significant increase in risk for any of the dementia outcomes studied. Their pooled all-cause dementia risk was 19% lower than that of current smokers. The researchers said further work should assess whether age at quitting or time since quitting is associated with dementia risk.
The review updated a 2015 evidence review and drew on studies published from January 2013 through Aug. 31, 2026. It examined clinically diagnosed dementia syndromes, rather than disease identified through biological markers. The findings were published in eClinicalMedicine.
The authors said the observational evidence does not establish that smoking caused dementia. Senior author Professor Blossom Stephan said brain health should be included in public discussion of smoking and quitting. Researchers also urged tobacco campaigns and cessation programs to address smoking's potential effects on brain health.
