Yes—but only in a population-level, probabilistic sense. The 45% estimate does not mean one person can reduce their dementia risk by 45% or guarantee prevention. The World Health Organization's July 2026 guidance says up to 45% of dementia risk is attributable to modifiable factors. "Modifiable" means potentially changeable through personal care, health services, public policy, or environmental improvements.
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Table of Contents
- What does the 45% estimate measure?
- Which factors are included?
- Why the percentages cannot simply be added
- How certain is the estimate?
- What can readers act on?
What does the 45% estimate measure?
The figure comes from the 2024 Lancet Commission's weighted population-attributable-fraction model. This method estimates the share of cases associated with selected risk factors across a population. The Lancet Commission estimated that 14 potentially modifiable factors together account for 45.3% of dementia cases.
That is a modelled estimate of prevention or delay potential, not the observed result of an intervention that eliminated every factor. The estimate also does not divide an individual's risk into a fixed 45% modifiable portion and a 55% unmodifiable portion. A person may develop dementia despite addressing every relevant factor, while another person with several factors may never develop it.
Which factors are included?
The 14 factors span different stages of life. Less education appears as an early-life factor. Midlife factors include hearing loss, high LDL cholesterol, depression, traumatic brain injury, inactivity, smoking, diabetes, hypertension, obesity, and excessive alcohol use.
Later-life factors include social isolation, air pollution, and untreated vision loss. The timing categories describe when evidence links each factor most strongly with dementia risk; they do not make the factors irrelevant at other ages. The Commission assigned the largest individual weighted shares to midlife hearing loss and high LDL cholesterol, at 7% each. Less education and late-life social isolation received 5% each.
Why the percentages cannot simply be added
Risk factors often occur together. For example, inactivity may cluster with diabetes, hypertension, obesity, or social isolation. Counting every association as completely independent would exaggerate their combined contribution.
The Commission therefore adjusted its calculation for clustering. It used data from 37,000 adults aged 45 or older in Norway's HUNT study; five components explained 54% of the variance among the factors. Even after adjustment, an individual factor's percentage should not be read as a personal risk-reduction promise. Treating hearing loss, for example, does not automatically subtract seven percentage points from one person's dementia risk.
How certain is the estimate?
The model assumes that the 14 factors cause dementia. The Commission cautioned that the size of some associations may be overestimated or underestimated, so the calculation does not prove that eliminating every factor would prevent exactly 45% of future cases. The evidence also has geographic limits. Much of it comes from high-income countries, while low- and middle-income countries remain under-represented.
Exposure patterns, health services, and environmental conditions may differ across populations. Some model inputs are narrower than others. The authors lacked a worldwide estimate for high LDL prevalence and used one cohort for that input. "Up to 45%" is therefore best understood as an estimate of potential, with meaningful uncertainty around it.
What can readers act on?
The estimate supports attention to several connected areas rather than one dementia-prevention product. A practical review can include: These actions operate at different levels.
Individuals can address some through daily choices and clinical care, while cleaner air, education, and access to hearing or vision services also depend on communities and public policy. The WHO guidance supports life-course risk reduction, but it does not recommend B or E vitamins, omega-3 supplements, or multivitamins for dementia risk reduction without a diagnosed deficiency.
- Regular physical activity
- Tobacco cessation and lower alcohol use
- A healthy diet
- Management of hypertension, diabetes, and cholesterol
- Attention to hearing and vision loss
