Dementia is now the leading cause of death in Australia. But why is it fatal?

Most of us know dementia – a broad term for several disorders involving declines in memory, language and thinking – can severely affect daily life.

But dementia is now the leading cause of death for Australians.

Earlier this month, data from the Australian Institute of Health and Welfare found 17,400 people died in 2023 due to dementia. This is 9.5% of all deaths.

But it can also be an associated factor in death, accounting for a further 15,000 deaths in 2023. This is considered dying with dementia.

Studies suggest dementia deaths may be even higher, as under-reporting on death certificates is common.

So, how does dementia actually lead to death?

How dementia progresses

Dementia is a neurodegenerative condition associated with progressive death of cells within the brain. The most common form is Alzheimer’s disease, which accounts for 60–70% of all cases.

People with dementia experience declines in cognitive function that interfere with their everyday life, including memory loss, difficulty communicating, or trouble thinking. They might also experience changes in their mood, behaviour or personality.

As dementia progresses, cell loss spreads throughout the brain. Eventually it reaches regions such as the brainstem, which are important for vital functions, such as breathing and swallowing.

In some cases, these effects on the brain can cause death. But they can also lead to other complications, which can then be fatal.

Secondary complications can be deadly

When swallowing becomes more difficult late in the disease, serious complications can develop.

People with dementia may accidentally inhale food or liquid into their lungs. This can lead to bacterial infections, such as aspiration pneumonia.

One 2019 review of 19 studies found people with dementia had double the risk of dying from pneumonia, compared to those without dementia.

Pneumonia caused more than one in four (29.69%) deaths of people with dementia. When the cause of death was confirmed via autopsy, rather than based on what was recorded on a death certificate, this was as high as one in two (49.98%).

Difficulties with swallowing can also lead to dehydration, weight loss and malnutrition. These can be further exacerbated by loss of appetite and lead to worse health and a weakened immune system.

This is why in its later stages, people with dementia often find it harder to fight off infections such as pneumonia or flu, and are more likely to experience complications.

Urinary tract infections also become more likely, due to incontinence and challenges maintaining personal hygiene. Communication difficulties may mean these infections go undetected.

Left untreated, infections can cause sepsis in severe cases. This is an extreme response to an infection, where the body attacks its own tissues and organs. It can lead to septic shock, organ failure and even death if not identified and treated.

Beyond infections, dementia can also increase frailty and impair balance and coordination. This can increase the risk of falls: people with dementia are twice as likely as those without the condition to have a fall.

And, when they do, they’re more likely to experience severe consequences, such as fractures, hospitalisation and even death.

Age plays a role

It is also important to acknowledge that age is the biggest risk factor for dementia. Among Australians aged 30–59, only one in 1,000 have dementia. Among those aged 85–89, this jumps to 210 in 1,000.

Older people may experience other age-related health conditions, such as heart disease, diabetes and high blood pressure (hypertension).

Dementia may make it more difficult to manage these conditions, leading to further health complications, such as stroke or heart attack. In these cases – when dementia is a contributing factor, but is not the primary cause of death – this is usually listed as dying with dementia.

In 2023, the leading causes of death among people who died with dementia were:

• heart disease (more than 1,900 deaths)
• stroke or other cerebrovascular disease (almost 1,500 deaths)
• COVID-19 (around 1,200 deaths)
• accidental falls (almost 1,100 deaths)
• diabetes (around 1,000 deaths).

Ways to reduce your risk

Without a medical breakthrough, the number of Australian dementia cases is projected to rise to more than one million by 2065.

The increase is partly due to our growing ageing population.

But dementia is not inevitable – and is not just a normal part of ageing.

The Lancet Commission on dementia, convened to review the evidence and provide recommendations on how to manage and prevent dementia, has identified 14 modifiable risk factors for dementia. These are:

• less education
• hearing loss
• high low-density lipoprotein (LDL) cholesterol
• depression
• traumatic brain injury
• physical inactivity
• diabetes
• smoking
• high blood pressure (hypertension)
• obesity
• drinking excessive alcohol
• social isolation
• exposure to air pollution
• vision loss.

By addressing these – at both the individual level and through government policies – it’s estimated we could prevent up to 45% of dementia cases. This could lead to us not only living longer, but living healthier for longer.