Meta-analysis of 61 cohort studies links current smoking to higher dementia risk

A systematic review and meta-analysis led by researchers at Curtin University in Australia has found that people who currently smoke are at higher risk of dementia than those who have never smoked. The risk increased with the number of cigarettes smoked each day, while former smokers did not show an overall excess risk. The work, published in eClinicalMedicine, is described as the most comprehensive update to the evidence in over a decade.

What the analysis covered

The team, led by Mario Siervo of the Dementia Center of Excellence at Curtin's enAble Institute and School of Population Health, pooled data from 61 prospective cohort studies involving about 2.8 million participants. It examined three outcomes: dementia from any cause, Alzheimer's disease and vascular dementia. Blossom Stephan, also of the Dementia Center of Excellence, is senior author.

Size of the associations

Compared with people who had never smoked, current smokers had:

• a 31% higher risk of all-cause dementia;
• a 40% higher risk of Alzheimer's disease;
• a 52% higher risk of vascular dementia.

A dose-response pattern also emerged. Smoking 10 cigarettes a day was associated with a 16% higher dementia risk, and 20 a day with a 34% higher risk, relative to never smoking. A graded relationship of this kind is one of the features researchers look for when judging whether an observed association may reflect a genuine biological effect, although it does not settle the question.

Former smokers

Former smokers had a lower dementia risk than people who kept smoking. Taken as a whole, their risk was not higher than that of people who had never smoked. This suggests that stopping may be linked to a meaningful reduction in risk, although the authors say the timing question remains open. They note that more work is needed to establish how the age at quitting, and the length of time since quitting, influence dementia risk.

Limits of the evidence

The authors stress that the analysis cannot show that smoking directly causes dementia. Cohort studies observe associations, and the pooled estimates depend on how each contributing study measured smoking and diagnosed dementia. The findings nonetheless add to a growing body of evidence that tobacco use belongs among the modifiable risk factors for cognitive decline.

Implications for tobacco control

The researchers point to a gap in policy. Smoking is listed as a dementia risk factor in three major international reports, yet Australia's National Tobacco Strategy 2023-2030 does not directly address dementia or brain health. They argue that antismoking campaigns, cigarette packet warnings and quit-smoking programmes could all include brain health, so that people understand the long-term risks of smoking and the benefits of quitting.

Co-author Tanya Buchanan, chief executive of Dementia Australia, described dementia risk reduction as a shared responsibility that needs action from all levels of government as well as information and research. Melissa Ledger of Cancer Council WA said the findings supported refreshing public health messaging. Her organisation ran what it believes was the first Australian smoking and brain health campaign earlier this year.

What comes next

For researchers, the immediate priority is to clarify how quitting age and years since quitting shape risk, which would help define when cessation offers the greatest benefit for brain health. Studies that test whether brain-health messaging changes quitting behaviour would show whether the policy proposals have practical value. The full analysis is reported in Siervo and colleagues' paper in eClinicalMedicine (DOI: 10.1016/j.eclinm.2026.104310).

Source: Smoking linked to higher risk of dementia (Medical Xpress, 10 November 2026).

Image: AI-generated illustration.