In 2024, the Lancet standing Commission on dementia published the most comprehensive update of what we know about preventable dementia. The headline finding: roughly 45% of dementia cases worldwide are linked to fourteen modifiable risk factors. Two new factors, high LDL cholesterol and untreated vision loss, were added to the original twelve from the 2020 report.
This article walks through all fourteen, what the evidence says, and what the practical action is for each.
A note before we start. "Modifiable risk factor" does not mean "if you fix this, you won't get dementia." It means there's a population-level association between the factor and dementia incidence, and reducing the factor is associated with reduced incidence. For an individual, personal genetic risk and dozens of other variables matter. Treat this list as a high-probability portfolio of decisions, not a checklist that buys immunity.
Which factors hit hardest at each life stage?
The Lancet Commission groups the factors by when in life they have the largest impact. We'll do the same.
Early-life factors
1. Less education
People who complete fewer years of formal education have a meaningfully higher dementia risk. The mechanism is cognitive reserve: more education builds more neural pathways, which compensates for damage later. We cover the science of cognitive reserve and how it's built in a separate piece. The action item, for adults reading this, isn't "go back and get a PhD." It's that continued cognitively demanding activity across your life builds reserve in a similar way. Languages, music, intellectually challenging hobbies, and complex work all qualify.
Midlife factors (roughly 45–65)
2. Hearing loss (untreated)
This is the single largest population-level risk factor in the Commission's analysis. Untreated hearing loss in midlife is associated with significantly elevated dementia risk. The 2023 ACHIEVE trial (Lin et al., Lancet) was the first large RCT to test hearing aids as a dementia-risk intervention; in older adults at elevated risk, hearing aids slowed cognitive decline by roughly 48% over three years.
Action: If you're over 50 and haven't had your hearing tested in three years, schedule it. If hearing aids are recommended, wear them.
3. High LDL cholesterol
Newly added in 2024. Mechanism: vascular damage to the brain. High LDL is one input to the broader cardiovascular-disease pathway, which is the single largest contributor to vascular dementia and a major contributor to mixed dementia.
Action: Know your number. Treat to current guidelines (which have shifted lower in recent years).
4. Hypertension
High blood pressure damages small vessels in the brain, contributing to white matter lesions and vascular dementia. Effects of treatment are reasonably well-established: aggressive blood pressure control in midlife is associated with reduced late-life dementia risk.
Action: Get your blood pressure measured at least annually. Treat systolic above 130 mmHg in midlife per current guidelines.
5. Obesity
Independent contributor to dementia risk, partly through cardiovascular pathways and partly through insulin signalling and inflammation.
Action: Standard advice, though the obesity-dementia link is one place where the Tier 1 brain health stack (exercise, sleep, diet) addresses multiple risk factors at once.
6. Diabetes
Type 2 diabetes roughly doubles dementia risk. Mechanism is multifactorial, vascular damage, insulin resistance in the brain, and inflammation. Tight glycaemic control reduces the elevated risk.
Action: If diagnosed, work with your physician to control HbA1c. If undiagnosed and at risk (family history, abdominal obesity, age over 45), get screened.
7. Excessive alcohol consumption
The Commission defines this threshold relatively strictly, more than 21 units a week. Heavy drinking accelerates brain volume loss visibly on MRI.
Action: If you're drinking more than two drinks a day, this is one of the highest-leverage changes you can make.
8. Traumatic brain injury
A single moderate-or-severe TBI roughly doubles long-term dementia risk. Multiple mild TBIs (concussions) compound. Risk persists for decades after the injury.
Action: Helmet use, fall prevention in older adults, awareness around contact sports, and, importantly, getting any concussion evaluated rather than "walking it off."
9. Smoking
Smokers have meaningfully elevated dementia risk. Stopping reduces risk substantially even in midlife. The mechanism is largely vascular, plus oxidative stress.
Action: If you smoke, quit. The dementia benefit is on top of the well-known cardiac and pulmonary benefits.
10. Depression
Untreated or recurrent depression in midlife is associated with elevated dementia risk. Whether depression is a cause of dementia or an early symptom of underlying neurodegeneration is debated; treating it is reasonable either way.
Action: If you have a history of depression that hasn't been addressed, address it. Effective treatments (therapy, SSRIs, exercise) are well-established.
Later-life factors (65+)
11. Social isolation
Older adults with smaller social networks and less frequent social contact have markedly higher dementia incidence. The effect size is comparable to many of the medical risk factors above.
Action: Maintain weekly contact with people you care about. Volunteer, join groups, prioritize community engagement. This is one of the most-overlooked entries on the list.
12. Physical inactivity
The Tier 1 brain-health intervention. Aerobic exercise has the strongest evidence base of any single behavioural intervention.
Action: 150 minutes a week of moderate aerobic activity. Anything that elevates your heart rate consistently, walking briskly counts.
13. Air pollution
Long-term exposure to particulate matter (PM2.5) is associated with elevated dementia risk. Mechanism likely involves neuroinflammation and vascular damage.
Action: Indoor air filtration in high-pollution areas, attention to outdoor exercise timing on bad-air days. Largely a policy and place-of-residence issue, with limited individual control.
14. Untreated vision loss
The newest addition (2024). Mechanism likely parallels hearing loss, sensory deprivation reduces cognitive engagement and accelerates decline.
Action: Annual eye exams. Treat cataracts, glaucoma, macular degeneration aggressively when diagnosed.
How should I think about my personal risk?
The 45% figure is a population-level theoretical maximum. Your personal benefit from acting on these factors depends on:
- Which factors apply to you. If you don't smoke and don't have diabetes, those rows on the list are already addressed.
- How aggressively you address them. The benefit scales with the gap between your current state and optimal.
- When in life you act. Earlier is better, but later is still meaningful for several factors.
A reasonable sequence for most readers:
- Know your numbers. Blood pressure, LDL, HbA1c, weight. If you don't know them, this is a single GP appointment.
- Get your hearing and vision checked.
- Audit the behavioural factors. Smoking, alcohol, exercise, sleep, social contact.
- Triage by leverage. Untreated hypertension is a bigger lever than fine-tuning your diet.
Not every factor is equally weighted, and not every factor applies to every person. The list is a menu, not a checklist.
What does this list *not* include?
It's worth noting what the Commission did not include, because plenty of marketing implies otherwise:
- Brain-training apps. Not on the list. The Commission acknowledges targeted cognitive training has supportive evidence (the ACTIVE trial in particular) but did not include it as a top-tier modifiable factor. The honest current state of the cognitive training evidence is that targeted protocols help, but they sit below the cardiovascular and sensory-health interventions in effect size.
- Specific supplements. Ginkgo, omega-3 monotherapy, B-complex megadosing in non-deficient adults, none made the list. The clinical-trial evidence remains weak or null.
- "Memory diets" beyond the broader Mediterranean / MIND patterns. Specific superfoods aren't on the list. The pattern is.
The bottom line
Fourteen factors. Address the ones that apply to you, in order of leverage. The hearing aid and the blood pressure medication and the four weekly walks are not glamorous, but they are what the evidence says works.
If you'd like the broader context, how this fits with cognitive reserve, exercise, sleep, and the role (and limits) of cognitive training, see our complete brain health guide. If you want to understand the underlying mechanism, memory 101 covers how memory actually works and where it fails.