Can dementia be prevented? what the research says

 

August 2026

Dementia prevention: what science knows today

For decades, dementia was widely viewed as an inevitable consequence of aging, shaped largely by genetics and beyond an individual’s control.

Emerging research now presents a more nuanced and increasingly hopeful picture.

Evidence from large-scale international studies suggests that a significant proportion of dementia cases may be preventable or delayed through earlier intervention, risk reduction, and sustained support for brain health across the lifespan.

The science of prevention

In July 2024, the Lancet Commission on Dementia Prevention, Intervention, and Care published its most comprehensive report update. The conclusion was striking: addressing 14 modifiable risk factors across the life course could prevent or delay around 45% of dementia cases worldwide.

That is not a minor finding. It means that nearly half of all projected dementia cases may not be inevitable.

The 2024 report built on previous Lancet Commission work, reaffirming 12 existing risk factors and adding two new ones: high LDL cholesterol in midlife and untreated vision loss in later life. The full list of modifiable risk factors now includes:

  • Less education in early life
  • Hearing loss
  • High blood pressure
  • Smoking
  • Obesity
  • Depression
  • Physical inactivity
  • Diabetes
  • Excessive alcohol consumption
  • Traumatic brain injury
  • Air pollution
  • Social isolation
  • Untreated vision loss (added 2024)
  • High LDL cholesterol (added 2024)

High LDL cholesterol accounts for an estimated 7% of dementia cases, and untreated vision loss accounts for approximately 2%, making them among the more significant individual contributors on the list. Both are conditions that are routinely screened for and, in many cases, treatable.

What this means for Canadians

The implications of risk reduction are not abstract. The Alzheimer Society of Canada's Landmark Study modelled three scenarios in which the onset of dementia across the Canadian population was delayed by one, five, or ten years. The results help quantify what prevention could mean at a national scale.

Even a one-year delay in dementia onset could result in almost 500,000 fewer new cases in Canada by 2050. A ten-year delay could avoid more than 4 million cases, and reduce caregiving demand by almost 1 billion hours a year.

Although science does not yet show how to delay dementia onset by a decade across an entire population, it does tell us that the actions to move that needle are already well understood, and that many of them are within reach for individuals, communities, and governments.

Risk reduction across the life course

One of the most important insights from the Lancet Commission's work is that dementia prevention is not a late-life concern. Risk accumulates across decades. The factors that increase risk in midlife, such as untreated high blood pressure, high LDL cholesterol, hearing loss, and obesity, can influence brain health outcomes 20 or 30 years later.

This means the window for meaningful action is wider than most people assume. The potential to prevent or better manage dementia increases significantly when action begins in childhood and continues throughout life, even in individuals with high genetic risk for dementia.

Research also supports the cumulative benefit of healthy habits. Engaging in four to five healthy lifestyle behaviors may reduce the risk of developing Alzheimer's dementia by 37% to 60%. And maintaining a cognitively active lifestyle in older age, such as reading, visiting libraries, writing, and playing games, may delay the onset of Alzheimer's dementia by as much as five years.

The Alzheimer Society of Canada has developed 12 evidence-based actions for brain health that Canadians can take at any age. These range from staying physically active and managing cardiovascular health to maintaining social connections and protecting hearing. None of them are groundbreaking on their own. Together, the evidence suggests they matter considerably.

The basis of urgency

With nearly one million Canadians projected to be living with dementia by 2030, and 1.7 million by 2050, the argument for investing in prevention is not complicated. Even modest improvements in risk reduction at a population level translate into hundreds of thousands of cases avoided, billions of dollars in costs reduced, and millions of caregiving hours that families do not have to provide.

The science says that nearly half of all dementia cases may be preventable. The question is whether Canada is prepared to treat that finding with the seriousness it deserves.