Nearly half of dementia is linked to things you can change
In 2024 the Lancet’s standing Commission on dementia, an international expert panel that reviews the evidence every few years, estimated that about 45% of dementia cases worldwide are linked to 14 risk factors that can be changed. In its 2020 report the figure was 40%, across 12 factors. The two new additions are untreated vision loss and high LDL cholesterol.[1][2]
The 14 factors span a whole life. Less education sits in early life. Hearing loss, high LDL cholesterol, depression, head injury, physical inactivity, diabetes, smoking, high blood pressure, obesity and heavy drinking sit in midlife. Social isolation, air pollution and vision loss sit in later life. Hearing loss and high LDL carry the largest shares, about 7% each.[1]
There is no single mechanism. Most of these factors damage the small blood vessels that feed the brain, add to inflammation, or reduce how much the brain is stimulated and used. Each one wears down the brain’s reserve, which is its ability to keep working well even as age-related changes build up.
The practical point is timing. Most of the changeable risk sits in your 40s, 50s and early 60s, long before memory slips. Several of the biggest levers can be measured with a routine blood test, a blood pressure reading, or a hearing and eye check. That is where prevention starts.
The people who ask me about dementia are usually the ones who watched a parent go through it. Family history is a good reason to start early. It still leaves most of these 14 factors in your hands.
What the Lancet Commission found
The Commission’s 45% comes from a calculation called a population attributable fraction. It asks a simple question: if a risk factor disappeared from the whole population, how many dementia cases would we expect to go with it? The panel then adjusted for overlap, because many people carry several factors at once.[1]
Two things follow. First, this is a population estimate, not a personal promise. Age and genes such as APOE4 still matter, and someone can do everything well and still develop dementia. Second, the authors describe these cases as delayed or prevented. Pushing dementia back by several years is still a real gain for a person and their family.
The 14 modifiable risk factors
Estimated share of dementia cases worldwide that could be prevented or delayed if each factor were removed, from the 2024 Lancet Commission.
| Risk factor | Life stage | Share of cases |
|---|---|---|
| Hearing loss | Midlife | 7% |
| High LDL cholesterol (new) | Midlife | 7% |
| Less education | Early life | 5% |
| Social isolation | Later life | 5% |
| Depression | Midlife | 3% |
| Traumatic brain injury | Midlife | 3% |
| Air pollution | Later life | 3% |
| Physical inactivity | Midlife | 2% |
| Diabetes | Midlife | 2% |
| Smoking | Midlife | 2% |
| High blood pressure | Midlife | 2% |
| Vision loss (new) | Later life | 2% |
| Obesity | Midlife | 1% |
| Excessive alcohol | Midlife | 1% |
The shares add up to more than 45% because the factors overlap. High blood pressure, diabetes, obesity and inactivity often travel together, so working on one usually moves several.
Hearing and vision are the most overlooked levers
Hearing loss is the largest single factor on the list, and it is the one people least expect. A 2023 meta-analysis of more than 126,000 people found hearing aid users had a 19% lower risk of long-term cognitive decline than people whose hearing loss went uncorrected.[4] The large ACHIEVE trial gives a more careful picture. Hearing aids did not slow decline across the whole group over three years, but they appeared to help the older, higher-risk participants.[3]
Vision follows the same pattern. Visual impairment is linked to a 38% higher dementia risk.[6] In one long-running cohort, people who had cataract surgery had a 29% lower dementia risk than those who left their cataracts untreated.[5] That study was observational, so it can’t prove cause.
The likely reason is fairly simple. A brain that gets less sound and less light has less to work with, has to strain to decode what it does get, and its owner often starts avoiding conversation and company. A hearing test and an eye check are cheap and dull, and well worth booking.
Your cholesterol matters to your brain too
High LDL cholesterol is one of the two new entries. In a UK study of more than 1.8 million people, LDL measured before age 65 was linked to dementia diagnosed more than ten years later, with risk rising about 17% for each step up in LDL.[7] The effect is modest per person, but it plays out over decades. That is why the Commission recommends checking and treating high LDL from about midlife.[1]
A standard lipid panel is a starting point. In clinic I often look further, because LDL can look acceptable while the number of cholesterol-carrying particles is high. I’ve written more about that in why ‘normal’ cholesterol can still hide risk.
Blood pressure and blood sugar feed the brain’s supply lines
The brain depends on a dense network of tiny blood vessels, and blood pressure and glucose both wear them down. In the Whitehall II cohort, a systolic blood pressure of 130 or higher at age 50 was linked to a 38% higher dementia risk, even though 130 sits below the usual cut-off for high blood pressure.[8] In the SPRINT MIND trial, tighter blood pressure control cut the risk of mild cognitive impairment by 19%.[9]
Blood sugar matters before diabetes is ever diagnosed. Among people without diabetes, a higher average glucose over the previous five years was linked to a higher dementia risk.[10] That is why I look at fasting insulin and HbA1c, not just a single fasting glucose.
Movement, mood and connection
You don’t need a gym habit to benefit. A 2025 meta-analysis found that 7,000 steps a day, compared with 2,000, was linked to a 38% lower dementia risk.[11]
Depression in later life is linked to nearly double the risk of dementia.[13] Sometimes low mood is an early sign of brain change rather than a cause, but either way it deserves proper care. Connection counts too. People with a small social network had a 59% higher dementia risk in a large meta-analysis.[14]
Alcohol, smoking, head knocks and air
In a 23-year follow-up of British civil servants, long-term drinking above about 14 UK units a week was linked to a higher dementia risk.[12] Smoking harms the same blood vessels that blood pressure does. Head injuries add up: in a Danish study of nearly three million people, risk climbed with each additional traumatic brain injury.[15] Air pollution is harder to control personally, though a meta-analysis still links it to a higher Alzheimer’s risk.[16] The useful steps are the plain ones: stop smoking, wear a helmet on the bike, and take falls seriously as you get older.
What the list leaves out
Sleep isn’t one of the 14, but it is hard to ignore. In the Whitehall II study, sleeping six hours or less at ages 50 and 60 was linked to a higher dementia risk, and persistent short sleep across midlife carried about a 30% higher risk.[17] Broken sleep from untreated sleep apnoea is worth ruling out.
Homocysteine is another. It is an amino acid that rises when B12 and folate status run low. In the VITACOG trial, older adults with mild cognitive impairment who took B vitamins showed slower brain shrinkage, and the benefit was concentrated in people whose homocysteine started high.[19][20] Those trials measured brain scans, not dementia diagnoses, so the lesson is to test first and act only on a real problem. A normal B12 result doesn’t always rule one out, which I explain in the B12 deficiency that hides behind a normal result.
Small changes work better together
The Finnish FINGER trial tested diet, exercise, brain training and vascular risk checks together in at-risk older adults. After two years, the combined program improved or held cognition compared with general health advice.[18] That fits what I see. Most people don’t need fourteen projects. They need to know which three or four of their own factors are the biggest, and start there.
For most people in their 40s and 50s, that means a blood pressure reading, a lipid panel, HbA1c and fasting insulin, B12 and homocysteine, a hearing test and an eye check. Our functional testing page sets out what we measure, and the brain fog and mood page explains how we work through cognitive symptoms.
Key Insights
Frequently asked questions
Can dementia really be prevented?
Not every case, but many may be delayed or prevented. The 2024 Lancet Commission estimates that about 45% of dementia cases worldwide are linked to 14 risk factors that can be changed, including hearing loss, high LDL cholesterol, high blood pressure, inactivity and smoking. This is a population estimate, so it doesn’t guarantee an outcome for any one person. Age and genes still play a part. Even so, pushing dementia back by several years is a meaningful gain.
What are the 14 modifiable risk factors for dementia?
They are less education in early life; hearing loss, high LDL cholesterol, depression, traumatic brain injury, physical inactivity, diabetes, smoking, high blood pressure, obesity and excessive alcohol in midlife; and social isolation, air pollution and vision loss in later life. Hearing loss and high LDL cholesterol carry the largest estimated shares, about 7% of cases each. Untreated vision loss and high LDL were added in 2024.
Do hearing aids lower the risk of dementia?
The evidence is encouraging but not settled. A 2023 meta-analysis found people who used hearing aids had a 19% lower risk of long-term cognitive decline than those with uncorrected hearing loss. The ACHIEVE trial found no difference over three years across its whole group, though hearing aids appeared to help older participants at higher risk. A hearing test is a simple, low-risk first step if you have noticed your hearing slipping.
At what age should I start reducing my dementia risk?
Midlife is the key window. Most of the changeable risk in the Lancet Commission’s list sits between your 40s and early 60s. In the Whitehall II study, blood pressure at age 50 was linked to dementia risk decades later, and LDL cholesterol measured before 65 was linked to dementia more than ten years on in a separate UK study. Starting early gives small changes the longest time to add up.
Ready to find answers?
If you want to know which of these factors matter most for you, we can measure them and build a plan around your own results.
References
- 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
- Livingston G, Huntley J, Sommerlad A, et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet. 2020;396(10248):413-446. doi:10.1016/S0140-6736(20)30367-6
- 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
- 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
- Lee CS, Gibbons LE, Lee AY, et al. Association between cataract extraction and development of dementia. JAMA Intern Med. 2022;182(2):134-141. doi:10.1001/jamainternmed.2021.6990
- Kuźma E, Littlejohns TJ, Khawaja AP, et al. Visual impairment, eye diseases, and dementia risk: a systematic review and meta-analysis. J Alzheimers Dis. 2021;83(3):1073-1087. doi:10.3233/JAD-210250
- Iwagami M, Qizilbash N, Gregson J, et al. Blood cholesterol and risk of dementia in more than 1.8 million people over two decades: a retrospective cohort study. Lancet Healthy Longev. 2021;2(8):e498-e506. doi:10.1016/S2666-7568(21)00150-1
- Abell JG, Kivimäki M, Dugravot A, et al. Association between systolic blood pressure and dementia in the Whitehall II cohort study: role of age, duration, and threshold used to define hypertension. Eur Heart J. 2018;39(33):3119-3125. doi:10.1093/eurheartj/ehy288
- SPRINT MIND Investigators for the SPRINT Research Group. Effect of intensive vs standard blood pressure control on probable dementia: a randomized clinical trial. JAMA. 2019;321(6):553-561. doi:10.1001/jama.2018.21442
- Crane PK, Walker R, Hubbard RA, et al. Glucose levels and risk of dementia. N Engl J Med. 2013;369(6):540-548. doi:10.1056/NEJMoa1215740
- Ding D, Nguyen B, Nau T, et al. Daily steps and health outcomes in adults: a systematic review and dose-response meta-analysis. Lancet Public Health. 2025;10(8):e668-e681. doi:10.1016/S2468-2667(25)00164-1
- Sabia S, Fayosse A, Dumurgier J, et al. Alcohol consumption and risk of dementia: 23 year follow-up of Whitehall II cohort study. BMJ. 2018;362:k2927. doi:10.1136/bmj.k2927
- Diniz BS, Butters MA, Albert SM, Dew MA, Reynolds CF 3rd. Late-life depression and risk of vascular dementia and Alzheimer’s disease: systematic review and meta-analysis of community-based cohort studies. Br J Psychiatry. 2013;202(5):329-335. doi:10.1192/bjp.bp.112.118307
- Penninkilampi R, Casey AN, Singh MF, Brodaty H. The association between social engagement, loneliness, and risk of dementia: a systematic review and meta-analysis. J Alzheimers Dis. 2018;66(4):1619-1633. doi:10.3233/JAD-180439
- Fann JR, Ribe AR, Pedersen HS, et al. Long-term risk of dementia among people with traumatic brain injury in Denmark: a population-based observational cohort study. Lancet Psychiatry. 2018;5(5):424-431. doi:10.1016/S2215-0366(18)30065-8
- Fu P, Yung KKL. Air pollution and Alzheimer’s disease: a systematic review and meta-analysis. J Alzheimers Dis. 2020;77(2):701-714. doi:10.3233/JAD-200483
- Sabia S, Fayosse A, Dumurgier J, et al. Association of sleep duration in middle and old age with incidence of dementia. Nat Commun. 2021;12(1):2289. doi:10.1038/s41467-021-22354-2
- Ngandu T, Lehtisalo J, Solomon A, et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial. Lancet. 2015;385(9984):2255-2263. doi:10.1016/S0140-6736(15)60461-5
- Smith AD, Smith SM, de Jager CA, et al. Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial. PLoS One. 2010;5(9):e12244. doi:10.1371/journal.pone.0012244
- Douaud G, Refsum H, de Jager CA, et al. Preventing Alzheimer’s disease-related gray matter atrophy by B-vitamin treatment. Proc Natl Acad Sci U S A. 2013;110(23):9523-9528. doi:10.1073/pnas.1301816110
