Half of New Zealand's dementia cases could be prevented – here's how to lower your risk

Woman hugging her elderly mother - stock photo
A senior lecturer in Psychiatry at the University of Auckland says there is "hope on the horizon" – pointing to evidence suggesting that if we were to eliminate 12 modifiable risk factors, half of all dementia cases could be prevented. Photo credit: Getty Images

With almost 70,000 Kiwis living with dementia today, many of us will know someone whose life has been permanently altered by the disease.

Sadly, that number is on track to more than double in the next quarter-century, with data showing New Zealand will be home to almost 170,000 people with dementia by 2050 on current trends.

But Alzheimer's NZ 2022 Fellow Dr Etuini Ma'u, a senior lecturer in Psychiatry at the University of Auckland, says there is "hope on the horizon" – pointing to evidence suggesting that if we were to eliminate 12 modifiable risk factors, half of all dementia cases could be prevented.

Dr Ma'u spoke in-depth about the science behind the disease and his work to slow the onset of dementia in an emotional episode of mental health podcast Are You Mental? in which host Mick Andrews explores the personal toll of his own father's journey with Alzheimer's. 

What even is dementia?

Dementia is roughly characterised by two symptoms, Dr Ma'u told Are You Mental?.

"One, you must have some sort of difficulty with how your brain processes information across a broad range of domains – memory orientation, your ability to sequence, to follow a recipe, to do complex things like driving or managing money. 

"And [two], those difficulties with aspects of your cognition have to be affecting your day-to-day functioning in some way."

With Alzheimer's, which accounts for two-thirds of all dementia cases, the classic signs usually revolve around a person's ability to retain and recall information.

"It's your ability to lay information down in your brain and form a memory, and then it's the ability of your brain to pull that information back out when you need it.

"With Alzheimer's, you tend to have difficulty actually forming a memory. In the moment, you're able to understand and process what's happening, but because you can't lay that memory down into a longer-term brain bank, you can no longer recall it." 

Alzheimer's is understood to be a result of a build-up of beta-amyloid and TAO proteins in the brain, which lead to the development of amyloid plaques, which are clusters that form in the spaces between nerve cells, and neurofibrillary tangles, which are knots of brain cells.

While it's not known whether these plaques and tangles are the cause of the dementia or just a marker, they cause inflammation, which exacerbates neurological issues.

"That inflammation results in cell death, so you start getting neuronal injury, and then that injury is big enough that you can actually see it on a scan and then at some point that injury results in so much cell death that it starts impacting on your brain's ability to function," Dr Ma'u says.

"Our brains are really good at compensating for subtle changes, so it's only when your brain's ability to compensate for those changes goes that you develop the symptoms." 

'NZ could prevent half of dementia'

Dr Ma'u says one of the reasons a cure for dementia hasn't yet been found is that there seems to be more focus on people who already have dementia, rather than on the changes in the brain 20-25 years prior - which lead to the onset of symptoms in the first place.

It's for this reason that Dr Ma'u has decided to focus his own research on dementia prevention.

"There is hope on the horizon. There's a lot of people researching this and they're now looking at targeting different potential underlying mechanisms for the causes of dementia. But for me, fundamentally, it's about preventing it in the first place," he told Are You Mental? 

"If we're targeting heart health and an active mind, then that's probably a much better way to conceptualise dementia than trying to develop a cure once someone has developed it.

"If we can delay onset by just five years, we would halve the number of people with dementia, because they would eventually end up dying of something else without ever developing the disease.

"It's a very hopeful way of looking at it, and we've shown that in New Zealand, if we can target 12 risk factors, we could prevent about half of all dementias."

Those risk factors fall into two broad categories: the things that reduce the risk of damage to your brain, and the things that improve your brain's ability to compensate for changes that occur. 

These 12 factors, identified in a 2020 Lancet Commission, are:

  • Limited education — continually learning improves brain function
  • Hearing loss or loss of smell
  • Hypertension/high cholesterol 
  • Obesity
  • Alcohol use
  • Head injuries (especially multiple injuries)
  • Smoking 
  • Depression
  • Social isolation
  • Physical inactivity
  • Diabetes 
  • Air pollution.

How to reduce your risk of dementia

The rule of thumb for combatting dementia is that anything that is good for your heart is good for your head. Dr Ma'u says the protection looking after your heart gives you is "phenomenal".

"You talk to people about the risks of heart attack and of stroke, and it doesn't seem to register with them. But you talk to them about the risk of dementia, and people are so fearful of that as a diagnosis because it's something that fundamentally cuts to the heart of who you are. 

"If that is something that kickstarts their healthy living journey, then hey."

Despite only weighing about a kilogram, our brains use about a fifth of our body's oxygen nutrient needs. That means anything that compromises blood flow to our brains is going to compromise our brain performance.

"Things like obesity, diabetes, smoking, alcohol, high blood pressure, depression, diet, exercise – all of those things can actually reduce your risk of developing dementia if you can address them," Dr Ma'u says.

"And then on the other side, it's about building your brain's resilience, building a cognitive reserve. And effectively, that centres around maintaining connectedness and social activities, keeping your mind active and ticking over – so education makes a difference." 

Interestingly, hearing loss is a "really big" factor in the likelihood of someone developing dementia, Dr Ma'u says.

"Your risk of dementia if you have hearing difficulties is almost double that of people without.

"We don't think it's because of any changes associated with the loss of hearing as such, but the fact that hearing is such a fundamental requirement for your ability to socially interact and to engage with others."

For those who fear they may already be beginning to develop dementia symptoms, Dr Ma'u says it's still not too late to do something about it. 

"Looking after your heart and brain health – those principles are also important if you have been diagnosed with dementia.

"There's very good evidence that actually looking after your heart and keeping an active and socially engaged mind, even after diagnosis, will help you to maintain your current level of functioning for longer."

The latest episode of Are You Mental? is available to listen to on Apple PodcastsSpotify, or wherever you get your podcasts.