Smoking and dementia risk explained

Smoking is linked to lots of medical conditions including:

• cancer
• heart disease
• high cholesterol
• high blood pressure
• dementia, particularly Alzheimer’s disease and vascular dementia.

Our brain cells need a good supply of blood to get the nutrients and oxygen they need to function.

When we smoke, our blood vessels become coated in a sticky substance. Over time, fatty lumps stick to this and builds up. This makes blood vessels  become narrower and weaker.

As a result, less blood can flow around our body properly, including to the brain. This increases our risk of conditions like heart disease, stroke and dementia.

Cigarette smoke also contains carbon monoxide. When we breathe this in, it takes the place of oxygen in our blood. So, our cells don’t get as much oxygen.

Over time, this can lead to brain cells dying and the brain shrinking. While this happens naturally as we get older, the brains of people who smoke shrink at a much faster rate. It particularly affects the areas of the brain involved in thinking and learning.

Yes. Stopping smoking can help protect brain health.

Quitting, even in mid‑life, can help slow down memory and thinking problems. Around 10 years after quitting, people’s dementia risk becomes similar to those who have never smoked.

But people who continue to smoke through their 40s and into later life are more likely to develop dementia.

For every 100 cases of dementia worldwide, almost half (45%) could be prevented or delayed. Two of those 45 cases are linked to smoking in midlife.

So, if nobody smoked, there would be one fewer case of dementia for every 100 people who develop it now.

Find out more: Addressing 14 health and lifestyle factors could prevent nearly half of global dementia cases - Alzheimer's Research UK

E-cigarettes and vapes haven’t been used for long enough for us to know their long-term effects on brain health and dementia risk. More research is needed.

If someone who smokes switches to e‑cigarettes, they are likely to reduce their exposure to harmful substances. Stopping smoking altogether is likely to be even better for overall health.

If you do not smoke, it’s best not to start vaping. Vapes can still expose you to substances that may harm your health.

Most of what we know about dementia risk comes from observational studies, which follow groups of people over time to look for patterns in health and lifestyle.

For example, studies like Insight 46 have followed people for decades to understand how health across life is linked to brain health and later on.

This is often the most practical way to study dementia risk. Many risk factors cannot be tested in trials in a fair or ethical way. Dementia also develops over many years, so studies can take a long time to show results.

Observational studies can show when something like our diet or occupation are linked to a higher or lower chance of dementia. But they cannot prove that something directly causes dementia, or that changing it will definitely reduce risk. These studies look at patterns across large groups, not what will happen to any one person.

Randomised controlled trials give stronger evidence because participants are assigned to different groups at random. This design makes it more likely that differences in outcomes, for example our risk of dementia, are caused by the intervention, for example a diet change, rather than by other factors.

But these studies are harder to do in dementia research. They often take many years and may test several changes at once, making results harder to interpret.

Newer trials are helping to build a clearer picture of what may support brain health. No single study can give a definite answer, but it is all research findings together that help us understand what is important for our brain health and risk of dementia.