Dementia Prevention: 14 Modifiable Risk Factors That Account for 45% of Cases

What Are the 14 Modifiable Risk Factors for Dementia?

The original 2017 Lancet Commission on dementia prevention identified 9 modifiable risk factors; the 2020 update expanded this to 12 by adding excessive alcohol consumption, traumatic brain injury (TBI), and air pollution. The 2024 update added two new factors—untreated vision loss and high LDL cholesterol—bringing the total to 14. Together, these risk factors are estimated to account for approximately 45% of global dementia cases, up from the 40% estimate in 2020, meaning that nearly half of all dementia could theoretically be prevented or delayed if these factors were fully addressed.

The risk factors are organized by life stage, reflecting the understanding that dementia prevention is a lifelong endeavor. In early life (up to age 45), lower educational attainment (population attributable fraction [PAF] 5%) and untreated vision loss (PAF 2%) are key modifiable factors. In midlife (ages 45–65), the major factors are hearing loss (PAF 7%—the single largest modifiable risk factor), high LDL cholesterol (PAF 7%), depression (PAF 3%), TBI (PAF 3%), physical inactivity (PAF 2%), diabetes (PAF 2%), and excessive alcohol consumption (PAF 1%). In later life (65+), smoking (PAF 2%), hypertension (PAF 2%), obesity (PAF 1%), social isolation (PAF 5%), and air pollution (PAF 3%) are the primary modifiable risks.

It is important to note that these risk factors interact with and amplify each other. For example, hearing loss contributes to social isolation, which independently increases dementia risk. Diabetes and hypertension damage cerebral blood vessels, reducing the brain's resilience to Alzheimer's pathology. Depression may both increase dementia risk and represent an early symptom of neurodegeneration. The cumulative and interactive nature of these factors means that multi-domain interventions addressing several risks simultaneously may be more effective than targeting individual factors in isolation.

Why Were Vision Loss and High LDL Cholesterol Added?

Untreated vision loss was added based on growing evidence that visual impairment significantly increases dementia risk through multiple pathways. A meta-analysis in JAMA Ophthalmology (2021) found that visual impairment was associated with a 47% increased risk of cognitive impairment and dementia. The mechanisms include reduced cognitive stimulation from the environment, decreased social engagement, reduced physical activity (due to mobility limitations), and potential direct effects on brain health through reduced visual processing demands. Critically, cataract surgery has been shown to reduce dementia risk, suggesting that the cognitive impact of vision loss is at least partially reversible. The Adult Changes in Thought (ACT) study found that cataract extraction was associated with a 30% lower hazard of dementia development.

High LDL cholesterol in midlife was included because of robust evidence linking dyslipidemia to both vascular dementia and Alzheimer's disease. Elevated LDL cholesterol promotes atherosclerosis in cerebral vessels, reducing blood flow and increasing the risk of subclinical brain infarcts that contribute to cognitive decline. Additionally, cholesterol metabolism is closely linked to amyloid-beta processing: the APOE ε4 allele, the strongest genetic risk factor for late-onset Alzheimer's disease, is primarily a cholesterol transport protein. Studies have shown that midlife total cholesterol levels above 240 mg/dL are associated with a 66% higher risk of Alzheimer's disease decades later.

The potential for statin therapy to reduce dementia risk remains an active area of research. Observational studies have shown mixed results, with some large cohort studies suggesting that statin use is associated with a 15–30% reduced dementia risk, while randomized controlled trials (which were not designed with dementia as a primary endpoint) have been inconclusive. The 2024 Lancet Commission emphasized that managing midlife LDL cholesterol through diet, exercise, and pharmacotherapy when indicated is recommended for cardiovascular health and may also provide cognitive benefits, though dedicated randomized trials are needed.

How Does Hearing Loss Increase Dementia Risk?

Age-related hearing loss affects approximately one-third of adults aged 65–74 and nearly half of those over 75. The association between hearing loss and dementia has been consistently demonstrated across multiple large prospective cohort studies, including the Baltimore Longitudinal Study of Aging (BLSA), which found that individuals with mild, moderate, and severe hearing loss had 2-fold, 3-fold, and 5-fold increased risk of incident dementia, respectively (Lin et al., 2011, Archives of Neurology). The relationship follows a dose-response pattern: each 10 dB increase in hearing loss is associated with approximately 20% increased dementia risk.

Three primary mechanisms have been proposed: (1) cognitive load—the effortful listening required with hearing loss diverts cognitive resources from memory and other processes; (2) brain structure changes—hearing deprivation accelerates temporal lobe atrophy, as shown in longitudinal MRI studies; and (3) social isolation—hearing loss leads to communication difficulties and withdrawal from social activities, and social isolation is itself an independent dementia risk factor. These mechanisms are not mutually exclusive and likely interact synergistically.

The ACHIEVE trial (Aging and Cognitive Health Evaluation in Elders), published in The Lancet in 2023, provided the first randomized controlled trial evidence that hearing intervention can slow cognitive decline. Among 977 community-dwelling adults aged 70–84 with untreated hearing loss, those randomized to receive hearing aids plus audiologic counseling showed 48% less cognitive decline over 3 years compared to a health education control group, specifically in a pre-specified subgroup of participants at higher risk for cognitive decline (from the ARIC cohort). This finding strongly supports hearing aid use as a dementia prevention strategy and has been incorporated into updated clinical practice guidelines by the WHO and multiple national health organizations.

What Can Individuals Do to Reduce Their Dementia Risk?

The multifactorial nature of dementia risk means that a comprehensive, lifespan approach to prevention is most effective. In early life, investment in education and cognitive development builds "cognitive reserve"—the brain's ability to cope with pathology before symptoms appear. Individuals with more education and cognitively stimulating occupations can tolerate more Alzheimer's pathology before manifesting clinical dementia. Throughout adulthood, maintaining cardiovascular health through regular physical activity (at least 150 minutes per week of moderate-intensity exercise), a heart-healthy diet (Mediterranean or MIND diet patterns), not smoking, and limiting alcohol consumption (no more than 14 units per week) addresses multiple risk factors simultaneously.

The FINGER trial (Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability), published in The Lancet in 2015, was the first large randomized controlled trial to demonstrate that a multi-domain lifestyle intervention could improve or maintain cognitive function in at-risk older adults. The 2-year intervention included nutritional guidance, physical exercise, cognitive training, and vascular risk factor monitoring. Results showed a 25% improvement in overall cognition and a 150% improvement in executive function compared to controls. The World-Wide FINGERS network now coordinates over 40 similar trials across six continents.

Specific actionable steps include: getting hearing tested and using hearing aids if prescribed (based on ACHIEVE trial evidence); getting regular eye exams and treating cataracts or other correctable vision problems; monitoring and controlling blood pressure (target below 130/80 mmHg based on SPRINT-MIND substudy evidence); managing LDL cholesterol per cardiovascular guidelines; maintaining social connections through community activities, volunteering, or group hobbies; wearing helmets during cycling and contact sports to prevent TBI; and minimizing exposure to air pollution (using air purifiers, avoiding exercising near heavy traffic). While no single intervention eliminates dementia risk, the cumulative impact of addressing multiple modifiable factors is substantial.