Alzheimer's Disease:
Risk Factors You Can Actually Change

Dementia is often framed as something that simply happens with age or genetics — largely outside anyone's control. The most authoritative body of evidence on this question, a standing international commission that periodically reviews the entire global evidence base, disagrees: it estimates that nearly half of dementia cases worldwide are linked to factors people can actually influence. This article lays out that full risk-factor picture — what's on the list, how much each factor is estimated to contribute, and which ones deserve the most attention.

The 14 modifiable risk factors

How to read this table

What "population attributable fraction" actually means. The population attributable fraction (PAF) is not the same as individual risk — it's an estimate of how much dementia incidence, across an entire population, would theoretically drop if a given risk factor were completely eliminated from that population. A 7% PAF for hearing loss doesn't mean any one person with hearing loss has a 7% chance of developing dementia because of it — it means that, across the whole population, roughly 7% of dementia cases are statistically linked to hearing loss as a contributing factor. These fractions also aren't strictly additive in a simple sense (some risk factors interact with and partially overlap each other), but the commission's methodology accounts for this, arriving at a combined estimate of ~45% of dementia cases being linked to all 14 factors together.

This is a standing, periodically updated international consensus, not a single study. This risk-factor framework comes from a standing Lancet Commission — a body of dementia researchers that periodically reviews the full global evidence base and updates its risk-factor list and estimates accordingly. The 2024 update added two new factors to the previous list of twelve: high LDL cholesterol in midlife and untreated vision loss in late life, and re-ran meta-analyses specifically for depression and hearing loss given new evidence since the prior report — which is also why air pollution shifted into the late-life category in this update, alongside social isolation and vision loss. This is meaningfully different from citing one observational study — it represents the current best synthesis of the field, regularly revised as new evidence emerges.

What you can actually change

The three largest individually-quantified factors: hearing, cholesterol, and education. Three factors are at or near the top of this list: midlife hearing loss and high midlife LDL cholesterol each at 7%, with less education in early life close behind at 5%. Education is the one factor on this list that can't be retroactively changed once someone reaches adulthood — but its underlying mechanism (building cognitive reserve) remains addressable throughout life through other routes, covered in Cognitive Reserve: Why Some Brains Age Better Than Others. Hearing loss and LDL cholesterol, by contrast, are both directly and immediately actionable at any adult age — hearing aids and lipid management are established, accessible interventions.

The cluster of cardiometabolic factors. Hypertension, obesity, diabetes, physical inactivity, and smoking together represent a cluster of interrelated cardiometabolic risk factors — the same category already covered with strong trial-level evidence in Vascular Health and the Brain. This overlap isn't a coincidence: several of the mechanisms linking these factors to dementia risk run through the same vascular and metabolic pathways, meaning that addressing one (for instance, blood pressure) often has beneficial knock-on effects on the others.

Depression and social isolation: smaller individual weight, but genuinely distinct pathways. Depression (3%) has a smaller individually-quantified contribution than some other factors, but it's included precisely because the evidence supporting it as an independent, non-overlapping risk pathway (not simply a symptom of early dementia itself) has strengthened enough to warrant its own dedicated meta-analysis in the 2024 update. Social isolation, at 5%, carries a genuinely larger individual weight than its "soft" framing sometimes suggests. Both get their own dedicated articles later in this series given how much nuance underlies each.

Recommendations

1. 1
   Don't treat this table as a checklist to eliminate all 14 factors perfectly

   The 45% figure describes a population-level ceiling on preventable risk, not a guarantee for any individual — genetics, age, and unmodifiable factors still play a substantial role.

2. 2
   Midlife is where most of the actionable factors concentrate

   The majority of the 14 factors sit in the midlife category specifically — this is a strong argument for taking cardiovascular and metabolic health seriously well before any cognitive symptoms would ever appear, not waiting until later life.

3. 3
   Hearing and vision are commonly overlooked but genuinely actionable

   Both sensory factors are often deprioritized relative to more "medical-sounding" risks like blood pressure, despite carrying real, quantified attributable fractions — a hearing or vision check is a low-friction, high-leverage addition to a longevity-focused health plan.

4. 4
   Cardiometabolic factors cluster together, so addressing one often helps several

   A patient working on blood pressure, weight, and physical activity simultaneously is addressing several line items on this list at once, not just one.

Practical notes

This risk-factor framework is the connective tissue for much of the rest of this series — nearly every remaining article in the Risk & Modifiable Factors and Practical Guide sections maps onto one or more lines in this table. Treating dementia risk as substantially modifiable, rather than fixed, is the evidence-backed starting point for everything that follows.