Alzheimer’s disease is a condition which effects the lives of many Australians, impacting relationships, self-esteem and the ability to live independently. In an ageing population, diseases that affect the brain are placing an increased strain on our community.
Whilst there is currently no guaranteed way to prevent Alzheimer’s, research over recent decades has revealed that a substantial proportion of dementia risk may be linked to factors that can be influenced throughout life. This raises an important question: can we reduce our risk of developing Alzheimer’s disease altogether?
What causes Alzheimer's disease?
Research has not identified a single cause of Alzheimer’s disease. Rather, it is considered the result of a complex interaction of factors, namely genetics, ageing, lifestyle and environmental factors that influence brain health over time.
Age remains the strongest known risk factor, with the likelihood of developing Alzheimer’s increasing significantly in later life. In Australia, the prevalence of dementia rises from < 1% of people aged 65-69 years to around 30% of those aged 90 years and over.
Genetics can also play an important role, particularly in individuals with a strong family history of the disease or those carrying certain genetic variants such as APOE ε4. Genetics alone however are not a certain predictor, and many individuals carrying these genes never go on to develop the disease.
This has led public health messaging to centre around the importance of modifiable risk factors – those aspects of health and lifestyle that we are capable of changing. Understanding these determinants and raising awareness amongst Australians remains one of Professor Ralph Martin’s key objectives.
Risk factors we can influence
The 2024 Lancet Commission estimated that up to 45% of dementia cases worldwide could potentially be prevented or delayed by addressing 14 modifiable risk factors across the life course. Whilst dementia is often viewed as an inevitable consequence of ageing, growing evidence suggests that the choices we make throughout life may influence our risk of developing the disease and even help delay the onset of symptoms.
Let’s take a closer look at some of these:
- Cardiovascular health
One of the strongest messages to emerge from Alzheimer's research is that what is good for the heart is also good for the brain.
The brain relies on a healthy network of blood vessels to deliver oxygen and nutrients to its billions of nerve cells. Conditions such as high blood pressure, high cholesterol, diabetes and obesity can damage these blood vessels over time, reducing blood flow and increasing the risk of both vascular dementia and Alzheimer's disease.
Protecting cardiovascular health throughout life is one of the most important steps people can take to support healthy brain ageing. Regular health checks, maintaining healthy blood pressure and cholesterol levels and managing chronic conditions can all contribute to reducing dementia risk.
- Physical activity
Regular physical activity is consistently supported as an important lifestyle strategy for maintaining brain health. A large body of research has linked regular physical activity with better cognitive health and a lower risk of dementia.
Exercise benefits the brain in several ways. It improves blood flow, supports cardiovascular health, reduces inflammation and may stimulate the growth of new connections between brain cells. Physical activity has also been associated with improvements in memory, mood and overall cognitive function.
Professor Martins' research has long supported the role of exercise as part of a broader approach to reducing dementia risk. His ongoing AU-ARROW clinical trial is investigating whether combining regular physical activity with dietary changes, cognitive training and management of cardiovascular risk factors can help preserve brain health in people at increased risk of Alzheimer's disease.
While researchers continue to investigate the optimal type, intensity and duration of exercise, current evidence suggests that maintaining an active lifestyle throughout adulthood is one of the most important steps people can take to support long-term brain health.
- Smoking
In addition to being identified in the Lancet Commission, a large meta-analysis of prospective cohort studies found that current smokers have a significantly higher risk of developing dementia than non-smokers. Researchers believe this increased risk is driven by several mechanisms, including damage to blood vessels, reduced cerebral blood flow, oxidative stress and chronic inflammation, all of which have been implicated in Alzheimer's disease.
Importantly, evidence suggests that smoking cessation is associated with a lower risk of dementia than continued smoking, reinforcing that it is never too late to make positive changes.
- Nutrition
Research has consistently found that dietary patterns rich in vegetables, fruit, wholegrains, legumes, fish and healthy fats are associated with better cognitive health and a lower risk of dementia. Rather than focusing on individual "superfoods", researchers increasingly recommend adopting an overall healthy dietary pattern, such as the Mediterranean or MIND diet.
Professor Martins' research has explored the relationship between nutrition, oxidative stress and Alzheimer's disease, contributing to a growing understanding of how diet may influence brain health across the lifespan. As this is a rapidly evolving area of research, we explore the science behind nutrition and brain health in greater detail throughout this series.
- Sleep
Sleep is increasingly recognised as an essential component of brain health. During sleep, the brain performs important housekeeping functions, including the removal of waste products that accumulate during the day.
Growing evidence suggests that poor sleep quality and untreated sleep disorders are associated with an increased risk of cognitive decline and dementia. Researchers believe disrupted sleep may impair the brain's ability to clear proteins such as beta-amyloid, although this remains an active area of investigation.
Prioritising good sleep habits and seeking treatment for persistent sleep disorders may therefore play an important role in supporting long-term brain health.
- Cognitive and Social Engagement
Keeping the brain active throughout life appears to be another important component of healthy ageing. Higher levels of education, ongoing learning and regular cognitive stimulation have all been associated with greater cognitive resilience.
Social engagement is equally important. Loneliness and social isolation have been identified as modifiable risk factors for dementia, with research suggesting that maintaining meaningful social connections may help preserve cognitive function later in life.
Activities such as reading, learning new skills, volunteering, participating in community groups and maintaining regular social interaction may all contribute to lifelong brain health. Whilst none of these activities can guarantee prevention, together they form part of a broader lifestyle approach supported by current research.
A Changing Perspective
For many years, Alzheimer's disease was viewed as an unavoidable consequence of growing older. Whilst age remains the greatest risk factor, research is increasingly showing that the story is far more complex.
The understanding of how lifestyle, genetics and overall health interact throughout life is reshaping the way researchers think about Alzheimer's disease. Although no single change can guarantee prevention, the evidence suggests that looking after our brains should begin long before symptoms appear.
Perhaps the most important message is not that Alzheimer's disease can always be prevented, but that many of the choices we make today may help support a healthier brain tomorrow. As research continues to evolve, so too does our opportunity to better understand, reduce and ultimately change the impact of this disease for future generations.
Professor Ralph Martins is an internationally recognised Alzheimer's disease researcher whose work focuses on dementia prevention, early diagnosis, healthy ageing and brain health. This article was developed in conversation with Professor Martins as part of the Research Insights series.
