Nearly Half of Dementia Cases Are Preventable: Lancet Commission Identifies 14 Modifiable Risk Factors

An estimated 7.4 million Americans aged 65 and older are now living with Alzheimer's disease (search)Search disease, according to the Alzheimer's Association's 2026 Alzheimer's Disease Facts and Figures report, and that number is projected to climb to nearly 13 million by 2050. Yet the same report found that while 99% of adults say brain health is as important as physical health, only 9% say they know enough about how to maintain it. This gap between concern and actionable knowledge is now being addressed by a growing body of research showing that dementia (search)Search disease is far from inevitable.

The 2024 Lancet Commission on Dementia (search)Search disease Prevention, Intervention, and Care concluded that roughly 45% of dementia cases are potentially preventable by addressing modifiable risk factors across the lifespan. "The research is clear that families have more control here than most people realize," said Frank Samson, Founder and CEO of Senior Care Authority (search)Search term. "And much of it involves building habits that are already within reach."

The 14 Modifiable Risk Factors

The Lancet Commission identified 14 modifiable risk factors that contribute to dementia (search)Search disease risk. These span the entire lifespan, from early-life low education to later-life social isolation. Laura Bojarskaite, PhD, a neuroscientist and sleep researcher at the University of Oslo, explained that "education likely builds cognitive reserve, giving the brain greater resilience against age-related pathology."

The full list includes: early-life low education, midlife hearing loss, high LDL cholesterol (search)Search target, depression, traumatic brain injury, hypertension, physical inactivity, diabetes, smoking, obesity, excessive alcohol consumption, later-life social isolation, untreated vision loss, and exposure to air pollution. High LDL cholesterol was added to the list for the first time in the 2024 update, accounting for an estimated 7% of dementia (search)Search disease cases globally.

Hearing Loss: The Single Biggest Modifiable Risk Factor

The Commission considers untreated hearing loss the single biggest modifiable risk factor for dementia (search)Search disease, accounting for approximately 7% of cases globally. Untreated vision loss accounts for an additional 2%. Together, they represent a larger share of preventable dementia risk than many lifestyle factors that receive far more attention.

A study published in The Lancet found that older adults at risk of dementia (search)Search disease who used hearing aids experienced 48% less cognitive decline over three years compared to peers who did not. Bojarskaite noted that hearing loss can increase cognitive load, reduce social engagement, and accelerate brain atrophy, emphasizing that "early hearing assessment and appropriate hearing aids are important interventions."

The Role of Physical Activity and Cardiovascular Health

Physical inactivity is one of the 14 modifiable dementia (search)Search disease risk factors identified by the Commission. Research published in Nature Medicine in 2025 found that physical inactivity in cognitively normal older adults was associated with faster buildup of tau protein (search)Search target, a key marker of Alzheimer's disease (search)Search disease pathology, and with faster cognitive decline overall. The protective benefit of movement appeared to reach a meaningful threshold at approximately 5,000 to 7,500 steps per day.

"Exercise is one of the most powerful brain-health interventions we know," Bojarskaite said. "Physical activity improves cardiovascular health, promotes neuroplasticity, and supports the growth and survival of neurons."

Hypertension, diabetes, and high LDL cholesterol (search)Search target are each identified as modifiable dementia (search)Search disease risk factors. Untreated high blood pressure has been identified in multiple large studies as one of the strongest predictors of future memory decline. "Elevated LDL contributes to vascular disease and may impair blood flow to the brain, increasing the risk of both vascular dementia and Alzheimer's disease (search)Search disease," Bojarskaite explained.

Sleep, Diet, and Social Connection

Research increasingly points to sleep as one of the brain's most important maintenance windows. During deep sleep, the brain undergoes a process that clears out toxic waste products, including proteins associated with Alzheimer's pathology. A study published in Neurology found that adults with disrupted sleep in midlife were more likely to experience cognitive decline a decade later.

Diet is one of the most consistently supported areas of dementia (search)Search disease risk research. A 2025 meta-analysis published in GeroScience found that greater adherence to the Mediterranean diet was associated with reduced risk of cognitive decline and Alzheimer's disease (search)Search disease. Research from Mass General Brigham, following more than 5,700 people over three decades, found that participants with high genetic risk for Alzheimer's who followed a Mediterranean-style diet reduced their probability of developing dementia by at least 35%.

Social isolation is among the Commission's 14 modifiable risk factors. A study published in Alzheimer's and Dementia (search)Search disease, the journal of the Alzheimer's Association, found that higher levels of social activity were associated with dementia onset occurring approximately five years later on average, compared to those with the lowest social engagement. "Loneliness and isolation are associated with faster cognitive decline and poorer mental and physical health," Bojarskaite said.

The Knowledge-to-Action Gap

Despite growing awareness, a study published on June 30, 2026, in The Lancet Healthy Longevity suggests there is a gap between people knowing how to prevent dementia (search)Search disease and actually putting those principles into practice. The authors note that while awareness campaigns can reach a large number of people, interactive approaches led by trusted community members appear to be the most effective way to elicit change.

According to the Alzheimer's Association, dementia (search)Search disease has more than 100 potential causes, and 18 to 20 percent of cases are highly treatable when identified. "Families frequently tell us they noticed changes months or even years before they sought help, and that they assumed what they were seeing was just part of getting older," Samson said. "That assumption can cost valuable time. A diagnosis is not the end of the conversation. It is often the beginning of finding real help."