For years, the number that circulated in brain health circles was 40%, the estimated share of preventable dementia cases if people addressed the right lifestyle factors.

That number just got revised upward.

preventable dementia cases

The 2024 Lancet Commission on Dementia Prevention, Intervention and Care updated its earlier 2020 analysis, adding two newly recognised risk factors and raising the combined estimate from 40% to 45% of dementia cases that could theoretically be prevented or delayed by addressing 14 modifiable risk factors. The commission expanded its list from 12 to 14 factors, identifying untreated vision loss and high LDL cholesterol as contributors that had not appeared in the previous report.

This means that nearly half of all dementia cases worldwide may be connected to factors you can actually do something about: how you sleep, what you eat, how much you move, what you hear, and how you manage the chronic conditions that accumulate quietly over decades.

Here is what changed, what it means in practice, and why this matters more than any drug trial currently in the headlines.

What the 2024 Lancet Commission Actually Found

The Lancet Commission on Dementia is not a single study. It is a working group of the world’s leading dementia researchers, assembled to synthesise the global evidence and produce consensus guidance. The first report was published in 2017. The second, and most widely cited, came in 2020, when the commission identified 12 modifiable risk factors responsible for an estimated 40% of dementia cases worldwide.

The 2024 update, published in The Lancet, extended that analysis. Two additional risk factors were added: untreated vision loss and high LDL cholesterol. These raised the combined modifiable fraction to an estimated 45% and joined the original 12: physical inactivity, smoking, excessive alcohol consumption, obesity, hypertension, diabetes, depression, hearing loss, traumatic brain injury, air pollution, limited education, and social isolation.

The revised population-attributable fraction represents the theoretical ceiling of what prevention could achieve. It assumes every person eliminates every one of these risk factors simultaneously, which is not a realistic target, but it defines the scale of what is biologically at stake.

What matters here is the direction of travel. Each update to this commission’s work has identified more preventable dementia cases, not fewer. As the science of dementia deepens, researchers keep discovering that lifestyle and environmental factors are more central to brain ageing than previously understood.

The Two New Risk Factors and Why They Were Added

Untreated Vision Loss

The connection between vision loss and cognitive decline follows a logic similar to hearing loss, which appeared in the 2020 report. When sensory input is reduced, the brain receives less stimulation. The cognitive demands of navigating the world with impaired senses may accelerate decline in vulnerable neural circuits. Several large cohort studies strengthened the association sufficiently for the commission to include it in the 2024 analysis.

The practical implication is clear, with appropriate caveats: regular eye examinations and correcting refractive errors with glasses, contact lenses, or cataract surgery are accessible interventions for most adults over 50. The commission identifies untreated vision loss as a modifiable risk factor. Addressing it is one piece of a broader prevention picture.

High LDL Cholesterol

The inclusion of LDL cholesterol in the 2024 report reflects growing evidence linking cardiovascular and cerebrovascular health to dementia risk. Higher LDL levels are associated with vascular injury to brain tissue and with conditions that disrupt the brain’s waste-clearance systems over time. Cardiovascular risk factors are biologically linked to brain vascular injury in ways that accumulate across decades.

This reinforces a pattern that runs through the entire Lancet analysis: midlife cardiovascular health is a long lever for late-life brain health. The decisions made in your 40s and 50s may not become visible in their consequences until your 70s.

What the Research Says: The Full Picture of 14 Risk Factors

The 14 modifiable risk factors identified by the 2024 Lancet Commission span the full lifespan, which is itself one of the report’s most important findings. Dementia prevention is not something you start at 70. The commission groups these factors across the life course:

Earlier life:

Midlife:

Later life:

The commission’s researchers estimated the population-attributable fraction for each individual factor. No single risk factor accounts for a large slice on its own. The 45% figure represents the combined theoretical effect: what modelling suggests could be eliminated if the entire population reduced exposure to all 14 simultaneously.

Two caveats the commission itself makes clearly: first, these risk factors overlap and interact (an obese person is more likely to have hypertension and diabetes). Second, reducing risk factors shifts probabilities, not certainties. Alzheimer’s and other dementias have genetic components, and some cases will occur regardless of lifestyle. The evidence base is becoming more refined, though still probabilistic.

Why This Matters More Than Drug Trials Right Now

The approval of lecanemab and donanemab as the first drugs to slow early Alzheimer’s progression generated significant coverage in 2023 and 2024. These are genuine advances. But they come with real limitations: both drugs work only in early-stage disease, require infusion treatments and clinical monitoring, and increase the risk of ARIA (amyloid-related imaging abnormalities), including brain swelling and microbleeds, which is why MRI monitoring is part of treatment. The benefit is a relative slowing of clinical decline over the trial period in eligible patients. While meaningful, it is modest and applies to a narrow population.

The Lancet Commission’s analysis operates at a different scale entirely. It is asking: what would happen to the global dementia burden if populations exercised more, treated hypertension earlier, wore hearing aids when needed, quit smoking, and kept LDL in a healthy range? The answer, based on current modelling, is that the number of preventable dementia cases worldwide could be substantially higher than current treatment rates suggest.

This does not diminish drug development. It puts it in context. For most adults reading this article, the lever is not a clinical trial. It is the accumulated effect of decisions made across decades.

Practical Action Steps

  1. Get your hearing and vision checked this year. Both are confirmed Lancet risk factors. Hearing aid use remains low in many populations. One Lancet article reported that only 14% of hearing-impaired U.S. adults aged 50 and older used hearing aids, with uptake far lower in some lower-resource settings. Routine eye exams and correcting vision impairment are straightforward interventions. Do not delay either.
  2. Ask your doctor for a full cardiovascular panel. High LDL cholesterol is the new addition to the 2024 report. Know your numbers. If your LDL is elevated, discuss whether dietary changes or medication are appropriate. This matters not just for your heart but as part of a broader brain health strategy.
  3. Address midlife blood pressure. Hypertension has appeared in every edition of the Lancet Commission. The SPRINT MIND trial found that intensive blood pressure management reduced the incidence of mild cognitive impairment, though the impact on dementia diagnosis itself was less clear-cut. Managing hypertension is not a secondary concern for brain health.
  4. Treat depression as a brain health issue, not just a mood issue. Depression appears in the 2024 report as it did in 2020. Whether depression causes dementia or shares upstream biological mechanisms with it remains an active research question. What is not debated is that it is a modifiable risk factor, and effective treatment exists.
  5. Use this list as a priority filter, not a panic list. The 14 risk factors are not equally weighted. Focus first on the ones most relevant to your current life stage and health situation, particularly those where evidence for benefit is strongest: physical activity, blood pressure, hearing, and social connection.

Conclusion

The 2024 Lancet Commission update moves the conversation forward without moving the goalposts. Two more modifiable risk factors. A revised estimate that now places nearly half of all dementia cases in the category of preventable dementia cases: delayable, reducible, addressable through lifestyle. A clearer picture of when in life each risk factor operates most powerfully.

Nearly half of dementia cases may be preventable. That figure will not mean much to someone who reads it and moves on. It will matter to someone who uses it as a framework: find the modifiable risks in your own life, address the ones you can, and build the habits that the research consistently associates with better brain ageing.

The commission publishes updated guidance so that it reaches clinicians, policymakers, and ultimately the people it is actually about. You are reading it. That is a reasonable place to start.

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This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making changes to your health routine.

Frequently Asked Questions

What does the 45% preventable figure actually mean?

It means researchers estimate that 45% of dementia cases worldwide are associated with 14 modifiable risk factors. In theory, if every person eliminated every one of these risk factors, that proportion of cases could be prevented or significantly delayed. In practice, the figure represents a population-level model, not a guarantee for any individual. Genetics and other non-modifiable factors still play a significant role.

What are the two new risk factors added in the 2024 Lancet Commission report?

The 2024 update added untreated vision loss and high LDL cholesterol. These joined 12 factors identified in the 2020 report, including physical inactivity, hypertension, hearing loss, smoking, excessive alcohol, obesity, diabetes, depression, social isolation, air pollution, traumatic brain injury, and limited education.

Is the 45% figure specifically about Alzheimer’s or all dementia?

It covers dementia broadly, which includes Alzheimer’s disease (the most common type), vascular dementia, and other forms. The Lancet Commission’s analysis applies to the overall dementia burden, not Alzheimer’s in isolation. Because Alzheimer’s accounts for the majority of dementia cases, the implications overlap substantially, but the 45% estimate should not be attributed to Alzheimer’s alone.

Should I wait for better drugs or focus on lifestyle now?

These are not competing options, but the honest framing is that approved drugs for Alzheimer’s currently work only in early-stage disease, require significant medical monitoring, and have produced modest benefit sizes in trial populations. Lifestyle interventions, applied consistently across decades, address the underlying conditions that raise risk in the first place. The two approaches operate at different points in the disease process. There is no research-backed reason to delay addressing modifiable risk factors while waiting for a pharmacological solution.

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Miguel Hernandez

Miguel Hernandez

Founder, The Memory Shield

Miguel founded The Memory Shield after watching his grandmother lose herself to Alzheimer's. His mission is to make the science of prevention accessible to everyone.