Can 45% of Dementia Cases Really Be Prevented? It's More Complicated Than That.

I recently came across a company advertising that up to 45% of dementia cases may be preventable.

I'd seen this statistic before in the medical literature. But seeing it in a consumer advertisement made me stop and think about how easily a well-intentioned message could be heard as something very different.

As a breast cancer survivor, I’ve felt the unintended weight of statements like that before. When public messaging focuses heavily on prevention, it’s easy for people to hear something very different than what was intended:

“If you got sick, you must have done something wrong.”

After my diagnosis, I did what I suspect many cancer patients do. I replayed my life, looking for the missing piece. Was it something I ate? Was it stress? An environmental exposure? Then came the well-meaning questions from others trying to make sense of it.

“Does it run in your family?”
“Did you eat organic?”

Most people aren’t trying to be insensitive. They’re looking for reassurance that if they make the “right” choices, it won’t happen to them. That’s a very human response.

But for the person living with the disease, those questions can quietly become guilt.

The statistic itself comes from excellent research and has appeared in peer-reviewed journals and expert consensus reports.¹ The problem wasn't the science—it was how easily the message could be misunderstood. That’s when I realized this was a conversation worth having. Discussions about reducing risk can easily be interpreted as assigning blame.

Dementia, like cancer, is extraordinarily complex. Age, genetics, biology, environmental exposures, vascular health, and simple chance all contribute to who develops disease and who doesn’t. Living a healthy lifestyle may lower your risk, but it can never eliminate that risk entirely. Likewise, developing dementia does not mean you failed to take care of yourself.

Once we are able to separate personal responsibility from population health, the research becomes far more encouraging than discouraging.

Where Does the 45% Figure Come From?

The statistic comes from the 2024 Lancet Commission on Dementia Prevention, Intervention, and Care.¹ After reviewing decades of research, the authors estimated that up to 45% of dementia cases might be delayed or prevented at the population level if 14 modifiable risk factors were addressed across the lifespan.

That does not mean 45% of individuals could avoid dementia simply by making different daily choices.

Many of these factors are deeply influenced by public policy, access to healthcare, education, environmental exposures, and socioeconomic conditions—not just personal decisions.

It’s also worth remembering that “modifiable” doesn’t always mean something a person can change now. We can’t go back and undo decades of untreated hearing loss, change the educational opportunities someone had as a child, or erase years of limited access to healthcare. These are factors researchers study because they help us understand risk across populations—not because they allow us to judge an individual’s story.

The 14 Modifiable Risk Factors Across the Lifespan¹

According to the 2024 Lancet Commission, addressing these factors could reduce or delay up to 45% of dementia cases at the population level:

• Less education
• Hearing loss
• High LDL cholesterol
• Depression
• Traumatic brain injury
• Physical inactivity
• Diabetes
• Smoking
• Hypertension
• Obesity
• Excessive alcohol use
• Social isolation
• Air pollution
• Vision loss

What the Evidence Shows Us

When we look closer at the science, some of the strongest evidence supports focusing on a few key interconnected areas:

• Hearing Health: Untreated hearing loss is one of the largest potentially modifiable risk factors identified.¹ Researchers believe the association is likely multifactorial—involving reduced sensory input to the brain, increased cognitive effort required to understand speech, and the social isolation that often accompanies hearing impairment. Although hearing intervention did not slow cognitive decline across the entire ACHIEVE study population, it did appear beneficial among participants already at greater risk. Observational studies have also associated hearing-aid use with a lower risk of cognitive decline and dementia.^2,3
• Cardiovascular Health: What’s good for the heart is generally good for the brain. Managing blood pressure, diabetes, cholesterol, and other vascular risk factors is an important part of protecting long-term brain health.¹
• Physical Activity and Sleep: Regular physical activity supports cardiovascular and metabolic health and is associated with a lower risk of cognitive decline and dementia.¹ Good-quality sleep is also essential for healthy brain function and is thought to support the brain’s natural waste-clearance system, known as the glymphatic system.⁴
• Cognitive and Social Engagement: Education, lifelong learning, and mentally stimulating activities have been associated with greater cognitive reserve—the brain’s ability to maintain cognitive function despite age-related or disease-related brain changes.⁵

Opportunity, Not Blame

Notice what this research is actually telling us.

It isn’t a list of reasons someone developed dementia. It’s a list of opportunities to improve brain health across our communities.

The goal of prevention research isn’t to make patients feel responsible for a disease they couldn’t completely control. It’s to identify the things we can improve—through better healthcare, better public health policy, and healthier habits—while recognizing that many people who develop dementia did everything “right.”

The purpose of prevention research is not to tell us who is to blame. It’s to help us understand where opportunities exist to improve brain health—for ourselves, our families, and future generations.

Research like this gives us more ways to think about protecting brain health. It should encourage us to make healthy choices where we can, without leaving people to wonder whether they somehow caused their own disease. You didn’t. Dementia is far more complex than that.

References

1. Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet. 2024;404(10452):572-628. doi:10.1016/S0140-6736(24)01296-0
2. Lin FR, Pike JR, Albert MS, et al. Hearing intervention versus health education control to reduce cognitive decline in older adults with hearing loss in the USA (ACHIEVE): a multicentre, randomised controlled trial. Lancet. 2023;402(10404):786-797. doi:10.1016/S0140-6736(23)01406-X
3. Yeo BSY, Song HJJMD, Toh EMS, et al. Association of hearing aids and cochlear implants with cognitive decline and dementia: a systematic review and meta-analysis. JAMA Neurol. 2023;80(2):134-141. doi:10.1001/jamaneurol.2022.4427
4. Nedergaard M, Goldman SA. Glymphatic failure as a final common pathway to dementia. Science. 2020;370(6512):50-56. doi:10.1126/science.abb8739
5. Stern Y, Arenaza-Urquijo EM, Bartrés-Faz D, et al. Whitepaper: defining and investigating cognitive reserve, brain reserve, and brain maintenance. Alzheimers Dement. 2020;16(9):1305-1311. doi:10.1016/j.jalz.2018.07.219