The most underrated dementia “prevention tool” might be sitting in your mouth, not your medicine cabinet.

Quick Take

• A major global analysis links roughly one-third of dementia cases to “peripheral” health problems outside the brain.
• Gum disease, chronic liver disease, hearing loss, vision loss, and type 2 diabetes sit near the top of the list.
• The Lancet Commission’s broader model puts 14 modifiable risks at about 45%, reinforcing prevention across the whole lifespan.
• The evidence comes largely from large observational datasets; it guides public health priorities more than it predicts any one person’s fate.

The “one-third” idea flips the dementia conversation from fear to leverage

Researchers aggregated results across more than 200 studies and asked a blunt question: how much dementia worldwide tracks with diseases that are not, strictly speaking, brain diseases? The estimate—about 33% of cases, roughly 18.8 million people—lands like a gut punch because it reframes responsibility and opportunity. It says dementia risk rides on the same everyday conditions doctors already treat, monitor, and sometimes ignore.

The practical tension sits right there: these numbers don’t mean gum disease “causes” dementia in a simple, courtroom way. They mean populations carry more dementia when those conditions run rampant, and populations carry less when they don’t. Conservative, common-sense readers will recognize the policy implication: you don’t need a moonshot drug to start cutting risk; you need consistent basics done well, earlier.

Why gums and livers show up in a brain disease: inflammation and shared plumbing

Periodontal disease ranks as a leading contributor in the peripheral breakdown, ahead of several conditions that get far more media attention. That surprises people because the mouth feels separate from the brain. It isn’t. Chronic gum inflammation can raise systemic inflammatory signals, and it often travels with smoking, poor diet, limited dental access, and uncontrolled diabetes—risk clusters that compound over decades. The liver fits a similar pattern: chronic liver disease often reflects metabolic trouble and long-term inflammation.

None of this should invite moralizing. It should invite triage. A neglected mouth can be a marker of a neglected body, and a neglected body can become a neglected mind. The cultural lesson is uncomfortable but useful: prevention isn’t glamorous. It’s showing up for cleanings, taking blood sugar seriously, and treating chronic illness before it turns into a pileup. That’s not nanny-state talk; it’s personal stewardship backed by data.

Hearing and vision: the “quiet” disabilities that isolate the brain

Hearing loss and vision loss appear prominently in both the peripheral analysis and the Lancet Commission’s modifiable risk framework. The pathway isn’t mystical. People who can’t hear well withdraw, misinterpret conversations, and stop participating. People who can’t see well drive less, walk less, and stay home more. Social isolation, reduced physical activity, and depression can follow, and those downstream effects can strain cognition over time. This is why simple devices—hearing aids and vision correction—keep showing up in prevention conversations.

The Commission’s July 2024 update underscored that prevention isn’t one big lever; it’s many smaller ones. It added high LDL cholesterol and untreated vision loss to reach 14 modifiable risks totaling about 45% of cases. The exact percentages matter less than the pattern: modest improvements across multiple systems can plausibly bend the curve. That approach aligns with fiscal reality too—small, scalable interventions beat endless spending on late-stage care.

Diabetes, kidneys, joints, and the domino effect of multimorbidity

Type 2 diabetes sits among top contributors in the peripheral estimate, and it rarely travels alone. Diabetes can bring vascular damage, kidney disease, and higher stroke risk—each with its own relationship to dementia. Osteoarthritis also appears on the list, a reminder that pain and immobility can shrink a person’s world. When movement declines, weight rises, sleep worsens, and blood pressure climbs. Dementia risk doesn’t arrive as a lightning bolt; it often arrives as a long chain of “manageable” problems left unmanaged.

Common sense says this chain should be broken where it’s cheapest and safest to do so. That means midlife checkups that don’t just record numbers but act on them. It means clinicians treating hearing and vision as brain health issues, not just quality-of-life add-ons. It means families treating dental visits as non-negotiable, the same way they treat oil changes—because skipping maintenance doesn’t save money; it just delays the bill with interest.

Watch:

What these estimates can and can’t promise, and how to use them without hype

These findings come from observational research and population-attributable fractions: powerful for public health planning, weaker for predicting one individual’s destiny. People can do “everything right” and still develop dementia, and some people do little prevention and remain cognitively sharp. That uncertainty doesn’t weaken the argument for action; it strengthens the case for humility and prioritization. The strongest takeaway is directional: reducing chronic disease burden likely reduces dementia burden too.

The best place to land is a grounded agenda: protect sensory function, treat cardiovascular and metabolic risks early, address smoking, and take oral health seriously. This avoids two traps—fatalism (“nothing can be done”) and snake-oil certainty (“do this one trick”). The real win is cultural: normalize brain health as whole-body health, because for millions of families, the future of memory may hinge on the most ordinary appointments.

Sources:

Nearly half of global dementia cases could be prevented or delayed by addressing 14 health and lifestyle factors, says new report
Researchers Reveal What’s Really Behind 18.8 Million Dementia Cases
Nearly half of dementia cases could be prevented or delayed by tackling 14 risk factors
AAIC: Lancet Commission reveals third of cases of dementia may be preventable
Dementia prevention, intervention, and care: 2020 report of the Lancet Commission
Dementia risk factors identified in new global report are all preventable; addressing them could reduce dementia rates by 45%
Risk Factors for Subjective Cognitive Decline Among Adults Aged ≥45 Years — United States, 2019–2020
Causes and Risk Factors