Hearing loss and dementia risk explained

There is strong evidence linking hearing loss in mid to late life with an increased risk of dementia.

Researchers do not yet know whether hearing loss directly causes dementia, or whether it leads to other changes that increase risk.

At the moment, there are two main explanations.

1. Changes in social connection and mood

People with hearing loss may find it harder to communicate and stay connected with others.

This can lead to loneliness, depression and social isolation. These are all linked to a higher risk of dementia.

2. Fewer chances to use hearing and thinking skills

Hearing helps us follow conversations and understand what is happening around us.

When hearing is reduced, the brain has to work harder to process sounds. This extra effort may take resources away from other thinking skills, like memory and attention. Over time this may affect how the brain works. This could make it more vulnerable to conditions like Alzheimer’s.

Hearing loss is one of the biggest risk factors for dementia we may be able to influence.

For every 100 cases of dementia worldwide, almost half (45%) could be prevented or delayed. Seven of those 45 cases are linked to untreated hearing loss in mid life. 

So, if everyone was able to manage or prevent hearing loss in midlife, there'd be seven 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

In some cases, changes in the brain linked to dementia may affect how sounds are processed.

For example some types of dementia, like primary progressive aphasia (PPA), can affect the parts of the brain involved in understanding and communicating speech

This means some types of hearing loss may sometimes be an early sign of dementia, rather than a cause.

Research suggests that people with hearing loss who use hearing aids may have a lower risk of dementia than those who do not manage their hearing loss.

The longer hearing loss is left untreated and the worse it becomes, the higher the risk may be.

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.