Blood pressure and dementia risk explained

Atherosclerosis

Over time high blood pressure makes our blood vessels narrower. This is called atherosclerosis. Narrow blood vessels can’t deliver as much oxygen and nutrients to our brain cells, so they may not get what they need to work properly. This increases the risk of dementia.

Increasing stroke risk

High blood pressure is the biggest risk factor for strokes. A stroke happens when blood flow to the brain is blocked or a blood vessel bursts. This damages brain cells.

One in three people that have had a stroke go on to develop vascular dementia.

High blood pressure can also damage small blood vessels deep in the brain. This can cause tiny bleeds (microbleeds). These don’t usually cause symptoms, but lots of these bleeds can damage the brain over time. This is called small vessel disease, and is another cause of vascular dementia.

Changes in brain structure

High blood pressure in midlife is linked to changes in the brain. This includes damage to small vessels, and parts of the brain getting smaller.

The area of our brain responsible for learning and memory, called the hippocampus, seems to be most affected by high blood pressure.

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

So, if everybody could effectively manage their blood pressure, there'd be two fewer cases 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

It’s important to test for and treat high blood pressure. This can help reduce the risk of dementia.

Medicines called antihypertensives are often used to treat high blood pressure.

Studies show that monitoring for, and treating high blood pressure can reduce the risk of developing dementia.^,, Current evidence suggests that all types of antihypertensive drugs seem to have similar effectiveness.

High blood pressure does not usually cause symptoms at first. This means many people do not realise they have it.

It is important to get your blood pressure checked regularly from mid life onwards so you can take steps to manage it if necessary.

You can have your blood pressure checked by a doctor or nurse at your GP surgery and at many pharmacies. You can also purchase an at-home blood pressure monitor.

Looking after your blood pressure is one way to help protect your brain.

Blood pressure can change as we get older. This varies from person to person.

Some research has found that a rapid drop in blood pressure, or very low blood pressure in later life, is seen more often in people who go on to develop dementia.

This is likely to be an early sign of changes in the brain, rather than being a cause of dementia itself.

Because of this, managing blood pressure in later life needs to be carefully balanced. It’s important to consider overall health, symptoms like dizziness or falls, and advice from a healthcare professional.

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.