7.2 million Americans have Alzheimer's dementia and 22% of seniors have MCI, but anti-amyloid therapy reaches only the amyloid-confirmed MCI and mild-dementia window — making the biomarker-confirmation pathway the real size of the market.
Alzheimer's disease is the most common cause of dementia. An estimated 7.2 million Americans aged 65 and older were living with Alzheimer's dementia in 2025, a figure projected to reach nearly 13 million by 2050 (Alzheimer's Association 2025 Facts and Figures). A further 22% of adults aged 65 and older have mild cognitive impairment (MCI) — the earlier clinical stage from which Alzheimer's dementia typically progresses. The disease is now staged along a continuum (preclinical/biomarker-positive and asymptomatic, MCI due to AD, and mild, moderate, and severe dementia), and that staging, not the raw prevalence figure, defines the commercially addressable population.
The two approved disease-modifying therapies (lecanemab, Leqembi, Eisai/Biogen; and donanemab, Kisunla, Eli Lilly) are indicated only for the MCI-due-to-AD and mild-dementia window, and only in patients with confirmed amyloid pathology. CLARITY AD showed lecanemab slowed cognitive decline (CDR-SB) by 27% at 18 months; TRAILBLAZER-ALZ 2 showed donanemab slowed decline by 35% in the low-medium tau population. Amyloid confirmation is therefore the true gate to therapy: historically via amyloid PET (Medicare coverage long limited to once per lifetime) or CSF, and now via the first FDA-cleared blood test — the Lumipulse G plasma pTau217/Aβ42 ratio (Fujirebio), cleared May 2025 for symptomatic patients aged 55 and older, with 91.7% positive and 97.3% negative concordance against amyloid PET or CSF. Scalable blood-based confirmation is the single biggest lever on how many of the eligible pool actually reach diagnosis.
Alzheimer's disease staging and the anti-amyloid-eligible window — United States, 2025
| Stage / Segment | US Population Context | Defining Feature | Anti-Amyloid DMT Eligibility | Diagnostic Gate |
|---|---|---|---|---|
| Preclinical AD | Large, largely unidentified | Amyloid-positive, cognitively normal | Not eligible — no approved indication | Biomarker / research only |
| MCI due to AD | Subset of the 22% of seniors with MCI | Cognitive complaint, function preserved | Eligible if amyloid-confirmed | Amyloid PET / CSF / plasma pTau-217 |
| Mild AD dementia | Early share of the 7.2M dementia pool | Mild functional decline | Eligible if amyloid-confirmed | Amyloid PET / CSF / plasma pTau-217 |
| Moderate–severe AD dementia | Majority of the 7.2M dementia pool | Substantial functional loss | Not eligible — outside DMT label | Clinical staging |
Sources: Alzheimer's Association 2025 Alzheimer's Disease Facts and Figures (prevalence, MCI); FDA Drugs@FDA (lecanemab, donanemab labels — MCI/mild-dementia indication); NEJM CLARITY AD (PMID 36449413); JAMA TRAILBLAZER-ALZ 2 (PMID 37459141); FDA clearance of Lumipulse G pTau217/Aβ42 plasma ratio (Fujirebio, May 2025).
What this assessment answers
Every section answers a named commercial question your team is asking, scoped to your asset.
Delivers
- Staging funnel from all-cause dementia to eligible pool
- MCI-due-to-AD sizing
- amyloid-positive fraction
- impact of scalable plasma pTau-217 testing on the diagnosis rate
Delivers
- Referral and cognitive-assessment pathway
- amyloid PET vs CSF vs plasma pTau-217
- Medicare PET coverage limits
- specialist and infusion-site capacity constraints
Delivers
- CDR-SB slowing comparison (CLARITY AD vs TRAILBLAZER-ALZ 2)
- ARIA-E/ARIA-H incidence by ApoE4 status
- MCI vs mild-dementia labeling
- dosing and amyloid-clearance stopping rule
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Commission This AssessmentWhat's inside
- The three-stage continuum (preclinical/biomarker-positive, MCI due to AD, and mild-to-severe dementia) that defines the addressable population
- Why staging, not the raw 7.2 million prevalence figure, determines who is eligible for anti-amyloid therapy
- The 7.2 million Americans aged 65+ living with Alzheimer's dementia in 2025, projected to reach nearly 13 million by 2050
- The additional 22% of adults 65+ with mild cognitive impairment, the pre-dementia pool feeding future dementia cases
- Why confirmed amyloid pathology, not clinical symptoms alone, is the true gate to lecanemab or donanemab therapy
- The historical reliance on amyloid PET (Medicare-limited to once per lifetime) and CSF testing before the blood-test era
- FDA's May 2025 clearance of the Lumipulse G plasma pTau217/Aβ42 ratio, the first blood test for AD amyloid, for patients 55 and older
- The test's 91.7% positive and 97.3% negative concordance against amyloid PET or CSF, and its potential to scale diagnosis
- Why lecanemab and donanemab are indicated only for the MCI-due-to-AD and mild-dementia window, not moderate-to-severe disease
- The efficacy gap between CLARITY AD's 27% CDR-SB slowing (lecanemab) and TRAILBLAZER-ALZ 2's 35% (donanemab, low-medium tau)
- How the funnel narrows from 7.2 million dementia patients and the 22% MCI pool down to the amyloid-confirmed, DMT-eligible population
- Why scalable plasma pTau-217 testing is the single biggest lever on how many eligible patients actually reach diagnosis
Included with every brief
How AXLRx builds this assessment
Prepared by MoatRx analysts.
Alzheimer's disease landscape is built from primary epidemiological sources, regulatory records, and peer-reviewed clinical literature. Epidemiological estimates carry source citations and are not modeled or inferred.
Key sources: Alzheimer's Association 2025 Alzheimer's Disease Facts and Figures (US prevalence and MCI); FDA Drugs@FDA labels and clearances (lecanemab, donanemab, and the Lumipulse G plasma pTau217/Aβ42 ratio); NEJM CLARITY AD (van Dyck et al. 2023, PMID 36449413); JAMA TRAILBLAZER-ALZ 2 (Sims et al. 2023, PMID 37459141).
- US prevalence (7.2M aged 65+) and MCI (22% of aged 65+) verified against Alzheimer's Association 2025 Facts and Figures
- First FDA-cleared AD blood test (Lumipulse G plasma pTau217/Aβ42 ratio, Fujirebio; symptomatic patients 55+) verified against FDA clearance, May 2025
- CLARITY AD lecanemab efficacy verified against NEJM primary publication (PMID 36449413)
- TRAILBLAZER-ALZ 2 donanemab efficacy verified against JAMA primary publication (PMID 37459141)
Frequently asked questions
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