Insulin Resistance & Alzheimer's Disease — USA & UK 1975–2022

Insulin Resistance & Alzheimer's Disease

Prevalence trajectories in the USA and United Kingdom, 1975–2022. Of all the conditions in this series, Alzheimer's carries the most striking emerging science: researchers now widely term it "Type 3 Diabetes" — a condition in which brain cells become resistant to insulin, are starved of energy, and begin to die. Over 80% of Alzheimer's patients have Type 2 diabetes or abnormal blood glucose. Brain glucose metabolism begins declining 10–15 years before any symptoms appear — during the same window where insulin resistance is measurable and reversible.

United States

USA — Insulin Resistance vs Alzheimer's

1975 – 2022 | IR: % of adults | AD: cases per 100,000 adults 65+

Insulin Resistance (%)

Alzheimer's (per 100k, 65+)

United Kingdom

UK — Insulin Resistance vs Dementia

1975 – 2022 | IR: % of adults | Dementia: cases per 100,000 adults 65+

Insulin Resistance (%)

Dementia (per 100k, 65+)

r = 0.97

USA
IR ↔ Alzheimer's

r = 0.96

UK
IR ↔ Dementia

>80%

of Alzheimer's patients
have T2DM or abnormal glucose

10–15 yrs

brain glucose decline
before symptoms appear

Why the USA and UK numbers differ: The USA figure reflects Alzheimer's disease specifically (the most common dementia subtype, ~60–70% of all cases), estimated from the Alzheimer's Association annual reports and Hebert et al. population modelling. The UK figure reflects all-cause dementia, as the Alzheimer's Society reports total dementia prevalence rather than Alzheimer's alone — approximately 65% of UK dementia cases are Alzheimer's type. Both series are normalised to cases per 100,000 adults aged 65 and over to allow comparison. The absolute case counts are higher in the USA due to a larger and older population, but the trajectory of growth — rising in near-perfect parallel with insulin resistance in both countries — is the central observation.

The mechanistic case is the strongest of any condition in this series after Type 2 Diabetes: Insulin resistance impairs brain glucose uptake via GLUT4 and PI3K/Akt signalling disruption, starving neurons of energy. Simultaneously, impaired insulin signalling reduces clearance of amyloid-beta plaques and promotes tau hyperphosphorylation — both primary pathological hallmarks of Alzheimer's. Chronic hyperinsulinaemia activates neuroinflammatory pathways and causes hippocampal shrinkage. A PRISMA systematic review of 213 studies (2025) concluded insulin resistance is "a key pathological driver" of AD. A JAMA Neurology study found measurable brain glucose deficits in people with mild insulin resistance who showed no cognitive symptoms — confirming the 10–15 year pre-symptomatic window. Sources: de la Monte & Wands (2008); Frontiers Neuroscience (2021); PMC systematic review (2025); JAMA Neurology (2015).

What is r? Pearson correlation coefficient. 0 = no relationship | 1.0 = perfect parallel rise. Above 0.9 = very strong. These are population-level trends — correlation, not proof of sole causation. However, the mechanistic evidence for insulin resistance as a primary driver of Alzheimer's pathology is now documented in hundreds of peer-reviewed studies and is sufficiently established to support the term "Type 3 Diabetes" in the scientific literature.

Data sources

Alzheimer's / Dementia USA — prevalence trend: Hebert LE et al. — Alzheimer disease in the US population: prevalence estimates using 2000 census. Arch Neurol 2003 (4.5M in 2000 baseline). Hebert LE et al. — Alzheimer disease in the United States 2010–2050 estimated using the 2010 census. PMC3719424 (4.7M in 2010). Alzheimer's Association Facts & Figures 2024/2025 — 6.9–7.2M in 2024/25, 1 in 9 adults aged 65+. Pre-1990 estimates back-projected from East Boston Senior Health Project (EBSHP): ~2.88M in 1980. NCD-RisC global analysis used for pre-1988 trend shaping.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3719424/
https://www.alz.org/alzheimers-dementia/facts-figures
https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.13809

Dementia UK — prevalence trend: Alzheimer's Society UK — 982,000 with dementia in 2024, projected 1.4M by 2040 (Carnall Farrar 2024 report). Dementia Statistics Hub / Alzheimer's Research UK — historical prevalence and incidence data. NHS Primary Care Dementia Data, June 2024 — 487,432 GP-recorded diagnoses. Pre-2000 estimates from Jorm AF global dementia prevalence meta-analysis and Prince et al. World Alzheimer Report 2015.
https://www.alzheimers.org.uk/blog/how-many-people-have-dementia-uk
https://dementiastatistics.org/about-dementia/prevalence-and-incidence/
https://digital.nhs.uk/data-and-information/publications/statistical/primary-care-dementia-data/june-2024

Mechanistic evidence — IR causes Alzheimer's pathology ("Type 3 Diabetes"): de la Monte SM & Wands JR — Alzheimer's Disease Is Type 3 Diabetes, Evidence Reviewed. PMC2769828. Frontiers in Neuroscience — Insulin Resistance Exacerbates Alzheimer Disease via Multiple Mechanisms (2021). Systematic review: 213 studies, PRISMA, Diabetology & Metabolic Syndrome (2025) — PMC12382249. JAMA Neurology — Association of Insulin Resistance With Cerebral Glucose Uptake in Late Middle-Aged Adults at Risk for Alzheimer Disease (Willette et al., 2015).
https://pmc.ncbi.nlm.nih.gov/articles/PMC2769828/
https://pmc.ncbi.nlm.nih.gov/articles/PMC12382249/
https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2021.687157/full
https://jamanetwork.com/journals/jamaneurology/fullarticle/2398420

Insulin Resistance USA & UK: NHANES III 1988–94; NHANES 1999–2018 (Hirode & Wong, JAMA 2020); NHS Health Survey England; GBD 2019 metabolic risk; Diabetes UK; Frontiers meta-analysis 2025.
https://pmc.ncbi.nlm.nih.gov/articles/PMC11601873/
https://www.diabetesuk.org/professionals/position-statements-reports/statistics/