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How does dementia cause death?

Explainer

Emma Taylor

On 09 December 2024

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After you or a loved one receive a diagnosis of dementia, it’s natural to have questions about the future. We understand that this can be an overwhelming time, so only read this information if you feel ready. It’s also OK if you decide you never want to read it.

For information about dementia, contact our Dementia Research Infoline or visit our webpage here for details of UK organisations that provide support for people affected by dementia.

Almost one million people in the UK are living with dementia today. And although new drugs are on the horizon, there are currently no treatments available in the NHS that can slow or stop the diseases that cause it. Once someone receives a diagnosis, there is no set progression or timeframe, and dementia affects everyone differently. But currently these diseases are incurable – although we’re working at pace to change that.

Alzheimer’s and other forms of dementia are the leading cause of death in the UK. But just six in 10 UK adults recognise that dementia can, and does in some cases, lead to death.

We recognise that this is a difficult topic to read about, but in this article, we’re going to discuss a question we’re often asked: how does dementia cause death?

A currently incurable condition

The word ‘dementia’ refers to a group of symptoms that includes confusion and memory loss. These symptoms are caused by diseases that damage the brain. However, the brain is responsible for more than just thought, memory and understanding. It also controls our bodily functions including breathing, blood circulation, and coughing.

As diseases like Alzheimer’s or vascular dementia progress, they damage more and more of the brain. This damage eventually affects areas of the brain that control the body, causing systems to go wrong and shut down, eventually leading to death.

There are a number of ways that this can happen:

Pneumonia

As dementia progresses, damage to the brain spreads, eventually reaching the brainstem. The brainstem forms the connection between the brain and spinal cord, and is responsible for controlling vital functions like breathing and swallowing.

As swallowing becomes increasingly difficult in the later stages of dementia, people are more likely to accidentally inhale food or drink. This can irritate the lungs, triggering infections and difficulty with breathing.

As coughing also becomes more difficult, people find it harder to get rid of the swallowed food or drink from their windpipe, making it more likely to cause infection in their lungs. ‘Aspiration pneumonia’ is a type of pneumonia caused by food or drink going down the windpipe instead of the food pipe and is one of the most common causes of death in people with dementia.

Starving and dehydration

There are several reasons why a person with dementia may stop eating and drinking. These include:

Loss of appetite caused by damage to the part of the brain that controls hunger and thirst.
Problems chewing and swallowing caused by damage to the brainstem.
Forgetting to eat, due to damage to the memory centres of the brain.

The body stops requiring as much food and drink during the last few weeks or months of life, so a loss of appetite is also normal for someone nearing the end of their life.

People with dementia can sometimes die directly as a result of a lack of food or drink, although this is rare. However, poor nutrition and weight loss can make someone more vulnerable to life-threatening illnesses and infections.

Severe urinary tract infections (UTIs)

There are several factors that lead to an increased risk of UTIs in people with dementia.

As dementia progresses, many people develop problems with incontinence. Many also struggle to maintain personal hygiene, and may forget to change their clothes or wash regularly. These things can lead to a build-up of bacteria in the urinary tract, leading to symptoms like a fever and a burning sensation when using the toilet. Dehydration can also increase the risk of UTIs, as going the toilet less often reduces the number of times that bacteria are flushed out of the body.

This means it’s common for people with dementia to develop urinary tract infections. Those living with advanced dementia may also not be able to communicate that they are experiencing symptoms, and so UTIs can be left unidentified and untreated. In some situations, severe UTIs can lead to cases of sepsis, which can be fatal.

Other conditions – e.g. diabetes – can go untreated

If people with dementia have other conditions, like diabetes or high blood pressure, as time goes on, they may forget to manage these with check-ups and medication. This can lead to further serious health complications. For example, untreated diabetes can damage blood vessels, brain cells and organs, while untreated high blood pressure can increase someone’s risk of a stroke or a heart attack.

Common viral infections

As we get older, our immune system’s ability to fight off illness starts to decline. Our bodies produce fewer antibodies, which are vital for detecting bugs like bacteria or viruses. Our cells also become slower to react to these bugs and destroy them. This makes our immune response less effective, and gives the bugs more opportunity to cause a severe infection.

As the diseases that cause dementia result in additional damage to our immune system, they speed up this decline. So, people with dementia are less able to fight off infection. This makes them more likely to experience severe complications resulting from illnesses like the ‘flu or COVID-19.

Falls

Common early symptoms of dementia can include problems with coordination and spatial awareness. Most people with dementia are at higher risk of falls, and are three times more likely to experience a serious injury after a fall and end up in hospital. Serious injuries like broken bones often require surgery and a long stay in hospital.

People with dementia are more likely to be admitted to intensive care units, and also to die within the first seven days in hospital than people without dementia. Because dementia weakens the body’s ability to recover, people with dementia are more likely to experience serious complications following surgery and in some situations this can lead to death.

After a fall, as well as pneumonia, people with dementia are also more likely to experience sepsis and surgical site bleeding than people without dementia and all of these conditions are also linked to the higher death rates.

Hope on the horizon

We realise that this is a difficult topic to discuss, so we want to end on a note of hope.

Millions of lives have been saved thanks to breakthroughs in medical research. Conditions that were once considered impossible to stop are now treatable, and in some cases, cured.

We’re on the path to achieving the same for people affected by dementia.

Over the past year, we’ve seen the emergence of the first treatments that target the underlying causes of Alzheimer’s disease. Although their effects are modest, with some side effects that can be serious, these drugs can slow down the rate at which symptoms get more severe, and will hopefully allow people to live independently for longer. And while these new drugs are not a cure, and are only appropriate for people affected by early Alzheimer’s disease, they represent an encouraging step forward. They show the diseases that cause dementia can be treated.

At Alzheimer’s Research UK, we will not rest until effective treatments for every form of dementia have been found, and are available to everyone who needs them.

With your help, we can change the ending for everyone affected by dementia. With your help, we can find a cure.

We know these topics are difficult to talk about. If you would like some more information about planning for the future, you can request your free information pack here.

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