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Why this works

16 modifiable risk factors, each backed by at least one published study. The attributable-risk figures come from the 2024 Lancet Commission and the studies it cites.

diet

Unhealthy diet— of population risk

Diets low in greens, fish and olive oil and high in processed food are associated with faster cognitive decline.

meta analysisNgandu T et al., The Lancet 2015Barnes LL et al., New England Journal of Medicine 2023

education

Less education1.7% of population risk

Fewer years of formal education is associated with a 40-60% higher dementia risk, likely through reduced cognitive reserve.

meta analysisLivingston G et al., The Lancet 2024Meng X et al., Psychological Medicine 2012

environment

Air pollution0.7% of population risk

Long-term exposure to fine particulate matter (PM2.5) increases dementia risk, even at levels common in US cities.

cohortLivingston G et al., The Lancet 2024Younan D et al., Annals of Neurology 2020

injury

Head injury1.0% of population risk

Even a single traumatic brain injury increases dementia risk by 37%. Risk rises with each additional injury.

cohortLivingston G et al., The Lancet 2024Fann JR et al., The Lancet Psychiatry 2018

metabolic

High LDL cholesterol0.7% of population risk

Elevated LDL cholesterol in midlife contributes to vascular damage that increases dementia risk.

cohortLivingston G et al., The Lancet 2024Thomas C et al., Neurology 2020
Diabetes or high blood sugar1.1% of population risk

Type 2 diabetes increases dementia risk by about 60% through vascular damage, inflammation and insulin resistance in the brain.

meta analysisLivingston G et al., The Lancet 2024Cheng G et al., Ageing Research Reviews 2012
Obesity0.7% of population risk

Midlife obesity (BMI 30+) increases dementia risk by 30-40% through inflammation, insulin resistance and vascular damage.

cohortLivingston G et al., The Lancet 2024Singh-Manoux A et al., BMJ 2018

movement

Physical inactivity1.7% of population risk

Regular physical activity reduces dementia risk by 30-40%. Walking counts.

commission reportLivingston G et al., The Lancet 2024Ngandu T et al., The Lancet 2015

sensory

Hearing loss8.2% of population risk

Untreated midlife hearing loss is the single largest modifiable risk factor identified by the 2024 Lancet Commission.

commission reportLivingston G et al., The Lancet 2024Lin FR et al., The Lancet 2023
Vision loss1.8% of population risk

Uncorrected vision impairment is associated with a 37% increased risk of cognitive decline.

meta analysisShang E et al., Journal of Neurology 2021

sleep

Sleep apnea— of population risk

Untreated obstructive sleep apnea increases dementia risk by about 26% through oxygen deprivation and sleep fragmentation.

meta analysisLeng Y et al., JAMA Neurology 2017Sabia S et al., Nature Communications 2021

social

Depression1.9% of population risk

Late-life depression doubles dementia risk. Treatment with therapy or medication reduces both depression and cognitive decline.

meta analysisLivingston G et al., The Lancet 2024Diniz BS et al., British Journal of Psychiatry 2013
Social isolation1.6% of population risk

Loneliness and lack of social contact increase dementia risk by about 50%.

meta analysisLivingston G et al., The Lancet 2024Kuiper JS et al., Ageing Research Reviews 2015

vascular

High blood pressure1.9% of population risk

Midlife hypertension damages small blood vessels in the brain, raising dementia risk. Intensive control reduces it.

commission reportLivingston G et al., The Lancet 2024Williamson JD et al., JAMA 2019
Smoking1.4% of population risk

Current smoking increases dementia risk by 30-40%. Quitting at any age reduces risk.

commission reportLivingston G et al., The Lancet 2024Zhong G et al., Journal of Alzheimer's Disease 2015
Excessive alcohol0.5% of population risk

Heavy drinking (more than 7 drinks per week) accelerates cognitive decline through direct neurotoxicity and vascular damage.

cohortLivingston G et al., The Lancet 2024Topiwala A et al., JAMA Neurology 2017

What we leave out

Brain-training games, supplements, and unproven diets are not on this list. The factors here are the ones the 2024 Lancet Commission and its cited studies identify as modifiable at the population level, with evidence from randomized trials or large prospective cohorts.