Smoking has long been recognized as a major risk factor for numerous health issues including cancer, lung disease and heart disease. But many smokers may not be aware that their habit also significantly raises their risk of developing dementia.
Leading health organisations now treat smoking as one of the clearest modifiable risk factors for cognitive decline and dementia.
How does smoking impact brain health and what is the evidence linking smoking to dementia?
Smoking and dementia: What the research says
The link between smoking and cognitive decline has been the subject of numerous studies.
Elevated dementia risk among smokers
- In 2015, a meta-analysis of 37 studies found that current smokers, when compared with never-smokers, had a 30% higher risk of developing dementia; the risk was 40% higher for Alzheimer's disease.
- Further meta-analysis revealed that current smokers have a 1.79-fold higher risk of developing Alzheimer’s disease and a 1.78-fold greater risk of vascular dementia than non-smokers.
- Long-term heavy smoking in mid-life has been shown to more than double the risk of dementia.
What happens to the brain?
According to the Alzheimer's Society, smoking increases the risk of dementia because: “Smoking increases the risk of vascular problems … Toxins in cigarette smoke also cause inflammation and stress to cells, which have both been linked to Alzheimer’s disease.”
Likewise, Alzheimer's Research UK points out that smoking reduces oxygen supply due to the carbon monoxide it contains and over time can “cause brain cells to die and the structure of our brain to shrink.” Smokers’ brains tend to shrink faster than those of the general population, especially in the regions responsible for thinking and learning.
Why does smoking raise dementia risk?
Researchers believe that there are several reasons why smoking increases dementia risk:
- Vascular damage & poor blood supply: Smoking harms blood vessels, raises blood pressure, and increases clotting risk, impairing the delivery of oxygen and nutrients to the brain. This contributes significantly to Vascular dementia.
- Oxidative stress & inflammation: Chemicals in cigarette smoke generate free radicals and inflammation, which damages neurons and accelerate brain aging.
- Reduced oxygenation: Carbon monoxide from smoke binds to haemoglobin in blood, reducing oxygen transport and so limiting oxygen supply to brain cells. Over time, this process can impair cognitive function and foster neurodegeneration.
- Long-term cumulative effects: The more someone smokes and the longer they smoke for, the greater the risk of dementia, suggesting a dose–response relationship.
Global implications
According to World Health Organization (WHO) and Alzheimer's Disease International (ADI), smoking may account for a substantial proportion of dementia cases worldwide. Their summary estimates that around 14% of Alzheimer’s cases globally are potentially attributable to smoking.
Dr Shekhar Saxena (Director, Mental Health and Substance Abuse, WHO) commented that, “Since there is currently no cure for dementia, public health interventions need to focus on prevention by changing modifiable risk factors like smoking.”
Dementia often develops over decades, making smoking, a changeable behaviour, a crucial target for prevention efforts.
Quitting smoking lowers the risk
The good news is that quitting smoking can reduce dementia risk. A longitudinal cohort study of more than 46,000 older men found that those who quit smoking had a significantly lower risk of dementia compared with those who continued.
Moreover, according to Alzheimer’s Research UK, people who quit smoking in mid-life may end up with a similar risk of dementia as those who never smoked.
In other words: while smoking increases risk, it is never too late to act.
- Smoking cessation should be seen not only as a way to prevent cancer, lung and heart disease but also as a powerful means to protect long-term brain health.
- Public-health policies aimed at reducing smoking rates could significantly reduce the future burden of dementia.
- Offering cessation support could become an important aspect of preventative care for dementia.
- Quitting smoking remains one of the most effective ways to reduce your risk of cognitive decline and dementia, even if you've smoked for many years.
The available evidence consistently links smoking to an increased risk of dementia. The damage to the brain has multiple causes including impaired vascular health, oxidative stress, reduced oxygenation, and accelerated brain shrinkage. As smoking is a modifiable behaviour, it is incredibly important that smokers are encouraged to quit.
