The growing burden of dementia in Aotearoa: Scope for prevention

Age is the greatest risk factor for dementia. Based solely on population ageing, the number of people with dementia in Aotearoa NZ (NZ) is expected to double in the next 20 years (Figure 1). However, it will almost triple in the same period for Māori and Pacific peoples due to their younger age structure currently.¹ Recent research shows the risk of dementia in Māori and Pacific peoples is 45%-80% higher compared to Pākeha in both young and late onset dementia due to the higher rates of risk factors in these ethnic groups. ^2,3

The 2024 Lancet Commission on dementia prevention, intervention, and care has identified 14 risk factors that, if completely eliminated, could prevent 45% of all dementias worldwide.⁴ These risk factors broadly fall into two groups. Firstly factors that result in damage to the brain: diabetes, high cholesterol, hypertension, smoking, obesity, air pollution, head injury, physical inactivity, high alcohol use, and untreated depression. Secondly, factors that reduce cognitive reserve, the brain’s ability to tolerate damage: low education, uncorrected hearing or vision loss, and social isolation. The potential for dementia prevention has been demonstrated to be higher in NZ, and even higher again in Māori and Pacific peoples compared to Europeans (Figure 1), due to the higher rates of risk factors compared to those used by the Lancet Commission.⁵

Our current NZ research demonstrates an association between social disadvantage and dementia. We have shown that the risk of developing dementia is 60% higher for people living in the most deprived areas of NZ compared to those in the least deprived areas.⁶ We have also shown that higher rates of risk factors for dementia are associated with increasing social disadvantage, regardless of ethnicity (Ma’u unpublished). Māori and Pacific peoples are overrepresented in the more disadvantaged areas of NZ society, with over 40% living in areas of high deprivation.⁷ These findings indicate that the higher risk and rates of dementia in Māori and Pacific peoples are not due to ethnicity per se but their overrepresentation in areas of high social disadvantage and poverty.

While completely eliminating risk factors is unlikely in the near future, even modest reductions in rates of risk factors can significantly reduce dementia prevalence. Indeed, recent estimates indicate that reducing 12 of the 14 risk factors in NZ by just 10% could result in 3,000 fewer people with dementia.⁸ Most risk factors are present across the life course and it is their incremental and cumulative damage to the brain that eventually lead to dementia. This highlights the importance of interventions to promote brain health in early life and midlife, even when the immediate dementia risk is deemed to be low. Furthermore, many risk factors are associated with other chronic disease processes such as stroke and heart disease, so the impacts of any risk factor reduction initiatives will provide other health benefits.

Many risk factors are conceptualised as something an individual can change but the realities are more complex and broader population-level approaches are required to appropriately address them. Many risk factors are associated with poverty and cluster in areas of greater social disadvantage. Effective policies and interventions will require a whole-of-government approach to address the health inequities associated with poverty and social disadvantage. Targeted legislative and public health measures reducing availability and marketing of alcohol, tobacco, and unhealthy food, in conjunction with optimised urban planning that promotes physical activity and social connection, can shift sociocultural norms and reduce risk at a population level.⁹