For a long time, dementia was seen as something that simply happened with age, or ran in families. You either got it or you didn't.
That view is changing. In 2024, the Lancet Commission on dementia prevention, intervention and care estimated that around 45 percent of dementia cases worldwide could be prevented or delayed by addressing 14 risk factors across a person's life.
In New Zealand, the Science Media Centre asked local experts what the findings mean here. Their answers are both sobering and hopeful. This article looks at what they said, why the potential for prevention may be even greater in New Zealand, and what individuals, whānau and communities can do.
For a broader look at the global evidence, including a major US lifestyle trial, see our companion article on preventing or delaying dementia.
What the Lancet Commission found
The 2024 Lancet Commission report added two new risk factors, high LDL cholesterol and untreated vision loss, to the 12 identified in its 2020 report.
The full list of 14 is:
less education
hearing loss
high LDL cholesterol
depression
traumatic brain injury
physical inactivity
diabetes
smoking
high blood pressure
obesity
excessive alcohol
social isolation
air pollution
untreated vision loss
According to the Science Media Centre, the Commission also set out 13 recommendations for governments and individuals, and called on governments to reduce inequalities by making healthy lifestyles achievable for everyone.
The 45 percent figure is a population estimate. It's what might be possible if all 14 risk factors were removed across a whole population. It doesn't mean any one person can cut their risk in half, and it doesn't mean people who develop dementia did something wrong.
Two ways risk factors affect the brain
Dr Etu Ma'u, a senior lecturer at the University of Auckland and consultant psychiatrist in mental health services for older people, offered a helpful way to think about the 14 risk factors. He described them as falling into two broad groups:
Factors that damage the brain. Diabetes, high cholesterol, high blood pressure, smoking, obesity, air pollution, head injury, physical inactivity, alcohol and depression.
Factors that affect cognitive reserve. Education, hearing, vision and social contact. Cognitive reserve is the brain's ability to cope with damage for longer before symptoms show.
Thinking about risk this way makes the advice clearer. Protecting the brain means looking after the heart and blood vessels, avoiding head injury and treating depression. Building reserve means staying mentally and socially active, and keeping hearing and eyesight in good shape.
Why prevention may matter even more in New Zealand
Dr Ma'u pointed out that New Zealand's population is ageing, and the number of people with dementia here is projected to more than double by 2050.
He also noted that New Zealand research suggests the potential for dementia prevention is likely higher here than the global estimate, and higher again for Māori and Pacific peoples. That's because some of the risk factors are more common in New Zealand than the worldwide figures the Lancet Commission used.
In other words, there's more to gain from prevention in Aotearoa, especially in the communities most affected.
It isn't only about personal choices
It's easy to read a list of risk factors as a to-do list for individuals. But Dr Ma'u cautioned that the reality is more complex. Many risk factors are present across a person's whole life, and many cluster around social disadvantage. That means population-level and public health approaches are needed alongside individual effort.
Some examples of what that can look like:
Education. Quality education for every child builds cognitive reserve for life.
Hearing and vision. Affordable hearing aids and regular eye tests make a real difference.
Health checks. Easy access to checks for blood pressure, cholesterol and diabetes.
Clean air. Policies that reduce air pollution, particularly in towns and cities.
Connected communities. Spaces and programmes that make it easier for older people to stay socially active.
Programmes also need to be designed with and for the communities they serve, including Māori and Pacific communities, so they're culturally relevant and actually reach the people who need them.
Head injury and contact sport
One risk factor has particular relevance in New Zealand: traumatic brain injury.
Dr Helen Murray, who leads the Brain Injury and Dementia Research Lab at the University of Auckland, noted that the Lancet review continues to support the link between traumatic brain injury, including repeated mild injuries, and dementia risk. With rugby and other contact sports so popular here, she highlighted the importance of reducing lifetime exposure to head impacts, for example through less contact training, shorter seasons and careful concussion management.
She also stressed an important balance. The Lancet review makes clear that sport is generally good for health, and sports players tend to have a lower overall risk of death. The goal is safer sport, not less of it.
What you can do
While wider change matters, there are still practical steps individuals and whānau can take:
Get your blood pressure, cholesterol and blood sugar checked, and follow your doctor's advice if they're high.
Have your hearing and eyes tested, and use hearing aids or glasses if you need them.
Stay active. Walking, dancing, gardening and team sports all count. Our article on why building muscle matters explains why strength is important as we age.
Don't smoke, and keep alcohol within recommended limits.
Protect your head. Wear a helmet for cycling and follow concussion guidance in sport.
Stay connected. Regular time with friends, whānau and community supports brain health.
Keep learning. Our article on why it's never too late to learn something new has ideas.
Look after your mental health. If you feel low for more than a couple of weeks, talk to your doctor.
Some risk factors, like genes and age, can't be changed. Our article on whether Alzheimer's is genetic explains more. But even people with a higher genetic risk can benefit from reducing the risks they can control.
Small, steady habits are easier to keep with a little support. Elli Cares helps older adults with reminders for medications, appointments and daily routines like a walk or a glass of water, and a simple daily wellbeing check-in. Whānau in the shared care circle can see how the day is going and offer encouragement from anywhere. See how Elli supports seniors and families.
Dementia is not inevitable
Dr Ma'u noted that recent new treatments for dementia offer small benefits that are outweighed, for now, by their cost and risk of serious side effects. In the absence of a cure, he argued, reducing risk must be a priority.
That's a message worth holding on to. Dementia isn't an inevitable part of ageing. For individuals, it means small, practical steps can make a difference. For communities and governments, it means there's a real opportunity to reduce the number of people affected, and to close the gaps between those most and least at risk.
Our article on debunking the most common dementia myths tackles some other common misunderstandings.
