Dementia remains one of the most challenging health conditions of later life, encompassing several progressive disorders that affect memory, thinking and the ability to function independently. Although age and genetics play important roles, research increasingly suggests that some dementia risk may be influenced across the life course.
A major 2024 report from the Lancet Commission estimated that approximately 45% of dementia cases worldwide could potentially be prevented or delayed by addressing 14 modifiable risk factors. This is a population-level estimate rather than a prediction that nearly half of dementia cases can definitely be prevented in any individual.
Guidance from the World Health Organization similarly emphasizes interventions that support cognitive and general health, while distinguishing established health recommendations from strategies that remain uncertain specifically for dementia prevention.
What prevention research suggests
Dementia develops through complex interactions among age, genetics, cardiovascular health, neurological disease, lifestyle, environment and other factors. Prevention research therefore focuses on reducing potentially modifiable risks rather than promising complete protection.
The Lancet Commission’s 14 factors span different periods of life and include lower education, hearing loss, high LDL cholesterol, depression, traumatic brain injury, physical inactivity, diabetes, smoking, hypertension, obesity, excessive alcohol consumption, social isolation, air pollution and untreated vision loss.
The estimated 45% population attributable fraction reflects the statistical contribution of these factors across populations. It should not be interpreted to mean that modifying all of them would necessarily prevent 45% of dementia cases in practice, because risk factors can overlap and associations are not always entirely causal.
Familiar cardiovascular risks also matter for the brain
Several factors associated with dementia are already important targets for cardiovascular and metabolic health. Physical activity, avoiding smoking, controlling hypertension and managing diabetes are supported by extensive evidence for their broader health benefits.
Excessive alcohol consumption is another recognized risk factor. Obesity and high LDL cholesterol in midlife have also been incorporated into the Lancet Commission’s dementia prevention framework.
Maintaining cardiovascular health may benefit the brain partly because vascular disease itself can contribute to cognitive impairment and dementia. However, dementia has multiple causes, and cardiovascular risk reduction cannot prevent every form of the condition.
Social isolation is another potentially modifiable factor. Observational research consistently links greater social isolation with higher dementia risk, although determining cause and effect is complicated because declining cognition can itself lead people to withdraw socially.
Maintaining relationships and meaningful social activity is nevertheless valuable for psychological and general health regardless of its precise effect on dementia risk.
Hearing, education and the environment
Hearing loss has become an important focus of dementia prevention research. The ACHIEVE randomized trial found that a hearing intervention did not significantly slow cognitive decline across the entire study population over three years.
However, in a prespecified group of older adults who entered the trial with greater risk of cognitive decline, the hearing intervention was associated with an approximately 48% reduction in the rate of cognitive decline compared with the health-education control intervention.
This distinction is important: the trial did not show that hearing aids reduce cognitive decline by nearly 50% in older adults generally, nor did it directly demonstrate that hearing treatment prevents dementia.
Several mechanisms could potentially connect hearing loss with cognitive health, including greater listening effort, changes in brain function and reduced social engagement. Their relative importance remains under investigation.
Education earlier in life is also associated with later dementia risk, potentially in part through cognitive reserve and socioeconomic pathways. Because educational opportunities are largely determined decades before dementia typically appears, this factor highlights the importance of population-level policies rather than placing responsibility entirely on older individuals.
Air pollution has also been associated with dementia risk. Reducing exposure can be difficult for individuals and often depends on transportation, environmental and public-health policies.
Vision and other emerging factors
Untreated vision loss was one of the two risk factors newly added by the 2024 Lancet Commission, alongside high LDL cholesterol. Observational evidence links visual impairment with higher dementia risk.
Correcting treatable vision problems has clear benefits for independence, safety and quality of life. However, evidence that treating vision impairment itself prevents dementia remains less certain, and prevention recommendations should reflect that distinction.
Sleep also has an important relationship with cognitive health. Sleep disorders, including obstructive sleep apnea, have been associated with cognitive impairment and dementia risk in observational research.
Yet association does not establish that treating sleep problems will prevent dementia. Sleep disorders should still be appropriately assessed and treated because of their established effects on health, functioning and quality of life.
Supplements are not a proven shortcut
Evidence does not support relying on vitamin or nutritional supplements as a general strategy for preventing dementia in people without a deficiency or another medical indication.
Trials of individual nutrients and supplements have produced mixed or generally unconvincing evidence for dementia prevention. This does not mean that vitamins, omega-3 fatty acids or other nutrients are unimportant; adequate nutrition remains essential, and supplementation may be appropriate when a deficiency or specific medical need exists.
It is also important not to treat all multivitamin evidence as uniformly negative. Some recent randomized trials have reported modest benefits in certain measures of cognition among older adults, but whether such findings translate into prevention of dementia remains uncertain.
Supplements can also cause adverse effects or interact with medications, particularly at high doses. They should therefore not be assumed to be harmless simply because their ingredients are available without prescription.
Managing risk across the lifespan
No single intervention can guarantee protection against dementia. Risk develops over decades, and different factors may matter at different stages of life.
For healthcare professionals, prevention can involve identifying and appropriately managing established health problems rather than applying the same checklist to everyone. Depending on the individual, priorities might include hypertension or diabetes management, smoking cessation, hearing or vision assessment, physical activity, depression care or reducing harmful alcohol consumption.
For individuals, many of the most reasonable steps are already recommended for general health: remaining physically active, avoiding smoking, limiting excessive alcohol consumption, managing cardiovascular and metabolic conditions and addressing hearing or vision problems when they occur.
Social connection and opportunities for cognitive engagement may also be worthwhile, while broader measures involving education and air quality require action beyond individual lifestyle choices.
Even with extensive risk-factor modification, dementia can still occur. Prevention research is therefore best understood as an effort to reduce probability and potentially delay disease onset rather than a formula for guaranteeing a dementia-free life.
At a population level, even a modest delay in dementia onset could have meaningful consequences as populations age. The emerging evidence therefore offers grounds for prevention efforts without implying that people who develop dementia failed to make the right lifestyle choices.
