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    Hidden Geography of Alzheimer's: Site Selection Insights

    Alzheimer's trials often rely on academic site networks that miss high-burden communities. Explore how geography, diagnosis gaps, and smarter feasibility data shape site selection.

    November 28, 2024
    ~20 min read
    By Kitsa Editorial Team

    An estimated 7.4 million Americans age 65 and older are living with Alzheimer's dementia today, a figure that could reach 13.8 million by 2060 [1]. The communities carrying the sharpest share of that burden are well-documented: older Black Americans are about twice as likely as older White Americans to develop Alzheimer's or other dementias, and older Hispanic Americans face roughly 1.5 times the risk [1]. And yet, across 26 years of Phase III Alzheimer's trials conducted in the United States, White participants constituted nearly 90% of enrolled populations, while Native American participants appeared in fewer than 3% of trials that reported racial data at all [2].

    That gap is not simply a recruitment problem. It is also, in part, a geography problem. The sites where Alzheimer's trials run are not consistently located where the disease burden is greatest, and the populations who carry the highest risk are not always within practical reach of the clinical research centers running the studies. Understanding why this pattern has persisted, and what it costs operationally and scientifically, is increasingly urgent now that disease-modifying therapies have finally reached patients.

    Why geography matters in Alzheimer's trial access

    7.4M
    Americans age 65 and older living with Alzheimer's dementia today [1]
    13.8M
    Projected Americans age 65 and older living with Alzheimer's dementia by 2060 [1]
    ~2x
    Higher Alzheimer's or dementia risk among older Black Americans compared with older White Americans [1]
    ~1.5x
    Higher Alzheimer's or dementia risk among older Hispanic Americans compared with older White Americans [1]
    ~90%
    Median White enrollment among U.S. Phase III Alzheimer's trials reporting race or ethnicity [2]
    <3%
    Trials reporting racial data in which Native American participants appeared [2]

    Why Geography Shapes Who Gets Into Alzheimer's Trials

    Site selection in Alzheimer's disease research has historically gravitated toward academic medical centers, large urban neurology practices, and established research networks. The logic is operationally sound: these institutions have trained coordinators, neuroimaging infrastructure, experienced principal investigators, and the regulatory systems that complex amyloid-targeting trials demand. They can obtain amyloid PET scans. They can run lumbar punctures for cerebrospinal fluid biomarker confirmation.

    What they often cannot do is enroll a representative sample of the population that actually develops Alzheimer's.

    A 2023 analysis published in Alzheimer's & Dementia [3] found that among 1,237 disease-modifying therapies tested in Alzheimer's and related dementia (ADRD) trials globally, only 11.6% had been studied in emerging economies, including just 2.0% in lower-middle-income countries. This despite the fact that low- and middle-income countries (LMICs) are projected to bear 65% of the global ADRD economic burden by 2050 [4]. The same concentration pattern plays out within the United States at a smaller geographic scale: researchers and clinical operations professionals who work across multiple Alzheimer's trial networks have documented that trial infrastructure congregates in established academic neurology hubs, while the communities at highest disease burden often remain structurally disconnected from enrollment pathways. A direct national mapping study of AD trial site distributions in the United States has not been published, but this observation is consistent with the broader literature on trial site concentration in academic centers [5, 6].

    The rural dimension is equally sharp. A study using national Medicare claims data found that risk-adjusted ADRD diagnostic incidence was actually higher in rural than in metropolitan counties, yet diagnosed prevalence appeared lower, strongly suggesting widespread underdiagnosis in rural areas rather than genuinely lower disease rates [5]. A 2025 scoping review published in Alzheimer's & Dementia: Translational Research & Clinical Interventions confirmed the pattern, noting that diagnostic gaps in underserved rural populations can distort prevalence data and confound study findings by making it appear that certain areas have lower dementia rates when the real difference is access to diagnosis [6].

    If patients are not diagnosed, they will not be referred to trials. And if trials are not located near the communities where patients live, referral alone cannot close the gap.

    Where Alzheimer's trial access narrows

    1
    Disease burden
    Millions of older adults living with Alzheimer's or at risk of ADRD
    2
    Diagnosis gap
    Rural, minority, and underserved patients are less likely to receive timely diagnosis
    3
    Referral gap
    Fewer than 1% of eligible U.S. patients may be referred into clinical research [8]
    4
    Site access gap
    Academic neurology hubs may be far from high-burden communities
    5
    Biomarker screen failure
    Amyloid PET, plasma amyloid, and comorbidity criteria reduce the candidate pool
    6
    Final enrollment
    Only a small share of biologically eligible patients reach randomization

    Alzheimer's recruitment failure is not one bottleneck. It is a sequence of diagnosis, referral, geography, biomarker, and site-capacity filters.

    The Enrollment Numbers Tell a Specific Story

    The scale of the mismatch between disease burden and trial access is not abstract. A 2024 USC roundtable convening 40 cross-sector Alzheimer's experts estimated that approximately 51,000 participants were needed to fully populate the 164 Alzheimer's clinical trials then in the active pipeline [7]. Against that demand, roughly 11,000 Americans successfully enrolled in clinical studies annually out of approximately 90 million who might be biologically eligible for preclinical, prodromal, or mild Alzheimer's trials [7]. Available secondary sources suggest fewer than 1% of eligible U.S. patients are ever referred into clinical research [8]; the primary data underlying this estimate come from multiple operational analyses of trial recruitment pipelines reviewed in that roundtable.

    The racial and ethnic picture within that enrollment funnel is sharper still. A 2025 preprint posted to medRxiv covering 88 U.S.-based Phase III Alzheimer's trials from 1997 to 2023 found that nearly half (49.3%) did not report participant race or ethnicity at all [2]. Among the trials that did report it, median enrollment was 0.9% for Asian or Pacific Islander participants, 4.5% for Black participants (ethnicity unspecified), 5.2% for Hispanic participants, and 0.4% for Native American participants, compared to nearly 90% for White participants [2]. Only 4.2% of trials conducted any subgroup analysis by race or ethnicity [2]. Because this analysis is a preprint awaiting peer review, these figures should be treated as preliminary, though their directional findings align with earlier peer-reviewed work documenting persistent minority underrepresentation in Alzheimer's research [9].

    This is not primarily a failure of patient interest. JAMA Network Open published a cross-sectional analysis of 5,945 screening participants in a preclinical Alzheimer's trial finding that Black, Hispanic, and Asian participants were more likely to be recruited from local efforts than White participants, who arrived through more distributed national campaigns, and were also more likely to fail screening after the first visit, even after adjusting for demographics [9]. Two additional data points from conference abstracts, where results are preliminary, reinforce this picture: evidence from the ENVISION aducanumab confirmatory trial reported a 90% screen failure rate among African American and Hispanic participants versus 75% in non-Hispanic White participants [10], and an enrollment pipeline analysis covering 490 prescreened participants across two active AD trials found only 1.6% were ultimately enrolled, with 38% of prescreened candidates failing for medical conditions or exclusionary medications, of which nearly half were not safety-critical [11].

    Each amyloid PET scan resulting in a screen failure carries a direct financial cost. A vendor-authored conference abstract from SiteRx described a 64% amyloid PET pass rate from patients identified through its data-driven pre-screening approach, compared to a 23% pass rate from conventional sources, with estimated PET scan cost savings of approximately $16,200 per patient [12]. This evidence is preliminary and vendor-reported; independent peer-reviewed validation has not been published. The directional finding, that upstream patient pre-selection quality affects PET confirmation rates, is consistent with the emerging blood-based biomarker prescreening literature.

    What Geographic Misalignment Costs a Trial

    Geography of site placement can materially influence these numbers. Sites serving populations with higher rates of undertreated cardiovascular comorbidities, which are more prevalent in certain demographic groups, will encounter more exclusionary comorbidity failures. Sites that rely on the same academic referral networks used for decades will draw from the same narrow population. The relationship between site placement choices and enrollment economics is plausible and operationally observed, even if its precise magnitude has not been isolated in peer-reviewed controlled comparisons.

    Why rural disease burden is easy to miss

    Rural ADRD access gap
    Lower claims-based diagnosis
    Rural counties may show lower diagnosed prevalence because fewer patients receive formal evaluation [5, 6]
    Higher adjusted diagnostic incidence
    Medicare claims data found risk-adjusted ADRD diagnostic incidence was higher in rural counties [5]
    Higher mortality per diagnosed patient
    Maryland geospatial analysis found high ADRD mortality zones in regions with low hospital accessibility [13]
    Site opportunity with infrastructure gap
    Rural areas may need satellite phlebotomy, mobile imaging, regional hospital partnerships, transportation support, and longer site qualification timelines

    Low diagnosed prevalence does not always mean low disease burden. In Alzheimer's research, it can mean low diagnostic access.

    Rural Alzheimer's: A Missed Site Opportunity

    The rural gap in Alzheimer's trial access deserves specific attention because it is both large and systematically underdocumented. A peer-reviewed geospatial study published in the Journal of Transport & Health in 2026, analyzing 422,735 ADRD patients in Maryland using Healthcare Cost and Utilization Project (HCUP) data, applied Getis-Ord G* hot spot analysis and geographically weighted regression to identify ZIP code-level areas where ADRD mortality rates were disproportionately high relative to diagnosed case counts [13]. Eastern and southern Maryland showed zones with high mortality per ADRD patient surrounded by similarly elevated-rate zones, while central Maryland, with greater hospital concentration, showed lower death rates per patient [13]. The authors concluded that underserved regions with limited hospital accessibility exhibited high ADRD mortality rates despite low diagnosis rates, consistent with substantial underdiagnosis rather than lower underlying disease burden [13]. This is a Maryland-specific analysis; whether the same spatial patterns hold nationally requires study at broader geographic scales.

    At the national level, Medicare claims data covering roughly 170 million person-years from 2008 to 2015 found that rural county residents diagnosed with ADRD experienced shorter survival compared to metropolitan county residents, a finding the researchers attributed to later-stage diagnosis rather than different underlying biology [5]. State-level NP practice authority compounds the diagnostic gap: a 2024 analysis found that states with restricted NP practice authority showed lower ADRD prevalence in Medicare claims data particularly in rural communities, while states granting NPs full independent practice authority showed a smaller rural-urban diagnostic gap [14].

    For site selection teams, rural areas are not conventionally attractive. They lack dense referral networks and immediate imaging access. But they hold large populations of older adults with measurable disease burden, low rates of prior trial exposure, and a genuine unmet need for research access. Whether the infrastructure gap is an obstacle or an opportunity depends heavily on how well a sponsor can characterize the local patient population before site commitment. Critically, rural site strategies often require structural adaptations that purely academic network approaches do not: satellite phlebotomy workflows, partnerships with mobile imaging providers or regional hospitals, transportation support programs, and longer lead times for site qualification. These are solvable operational problems, but they require planning that begins at the feasibility stage, not after activation.

    The LMIC Problem and What It Reveals About Site Selection Logic

    At the global level, the same calculus that drives site selection toward established academic centers in high-income countries systematically excludes the regions where Alzheimer's is growing fastest.

    The 2023 Alzheimer's & Dementia analysis [3] found that North America and Western Europe accounted for the overwhelming majority of ADRD trial sites globally. Sub-Saharan Africa, Southeast Asia, and Latin America, regions where dementia prevalence is rising sharply and where genetic and environmental risk factor profiles differ meaningfully from Northern European populations, hosted a tiny fraction of registered trial activity. Identified barriers included insufficient research infrastructure, low industry presence, regulatory obstacles, and limited access to neuroimaging [3].

    A 2022 Lancet eClinicalMedicine analysis estimated the global economic burden of ADRD at $2.8 trillion in 2019, projected to reach $16.9 trillion by 2050, with LMICs accounting for 65% of that future burden [4]. Trials that do not enroll from these populations produce efficacy and safety data of limited generalizability to the patients who will ultimately carry the largest share of the disease.

    This is both an equity and a scientific argument. A 2015 analysis of multi-national Alzheimer's trials published in Alzheimer's Research & Therapy found that disease progression and its measurement differed across geographic regions within the same trial, with population heterogeneity at baseline translating into real differences in outcome measurement [15]. When site selection consistently skews toward demographically narrow populations, sponsors may not discover these differences until post-approval.

    How biomarker requirements become a site-selection variable

    [1]
    Amyloid PET confirmation
    Expensive confirmatory step where poor pre-selection increases screen failure cost
    [2]
    Plasma amyloid eligibility
    AHEAD 3-45 plasma biomarker screening found Black and Hispanic participants were less likely to meet amyloid thresholds [16]
    [3]
    Comorbidity exclusion risk
    Sites serving high-comorbidity populations may see more exclusionary medical failures
    [4]
    Blood-based prescreening
    PROGRESS-AD reported reducing amyloid confirmation screen failure to 9.9% using blood-based biomarkers [17]
    [5]
    Feasibility implication
    Sponsors should model biomarker screen failure risk by catchment area before activation

    Biomarker eligibility is not only a lab issue. It changes which sites can enroll efficiently and which populations are most likely to screen fail.

    Biomarker Eligibility as a Geographic Filter

    One mechanism through which site selection quietly shapes enrollment is the interaction between amyloid eligibility criteria and population-level biomarker variation.

    A 2024 peer-reviewed study published in Alzheimer's & Dementia by Molina-Henry et al. examined plasma biomarker screening data from 4,905 participants across 75 AHEAD 3-45 study sites [16]. The researchers found that people who identified as Black or Hispanic were less likely to meet the plasma amyloid eligibility thresholds required to continue in screening, even though they face higher risk for Alzheimer's and related dementias. Among non-Hispanic Black participants, 24.7% were plasma-eligible, compared to higher rates among non-Hispanic White participants [16]. The authors noted that this difference in biomarker eligibility may reflect underlying variation in amyloid accumulation patterns across populations at this early preclinical stage, and raised questions about whether eligibility thresholds developed largely in studies with predominantly White participants adequately capture disease biology across all groups [16]. These are active research questions; the mechanisms driving group-level differences in amyloid accumulation remain incompletely understood and warrant further study before definitive conclusions about threshold design are drawn.

    For site selection strategy, the operational implication is clear regardless of mechanism: sites serving predominantly minority populations will encounter higher biomarker screen failure rates, and sponsors who do not account for this during feasibility analysis will underestimate screen failure rates and overestimate enrollment velocity. This is a solvable planning problem if it is anticipated, and a costly surprise if it is not.

    Blood-based biomarker prescreening has emerged as a partial mitigation. A Phase 2 trial incorporating plasma pTau181 and PrecivityAD assays into the prescreening pipeline for PROGRESS-AD reported reducing the screen failure rate for amyloid confirmation to 9.9% [17]. This is conference-level evidence from a single phase 2 study and should be treated as preliminary. Deploying blood-based prescreening assays at sites serving diverse populations may improve the proportion of minority participants who reach randomization, but larger studies are needed to confirm this in practice.

    Regulatory and Documentation Considerations

    The regulatory context for trial diversity in Alzheimer's research involves two distinct frameworks that are sometimes conflated.

    The Food and Drug Omnibus Reform Act of 2022 (FDORA), Section 3601, created the statutory framework for Diversity Action Plans (DAPs), requiring sponsors of pivotal clinical studies to submit DAPs to the Secretary of Health and Human Services [23]. The statute ties applicability to studies whose enrollment begins 180 days after publication of the required final DAP implementation guidance. The June 2024 FDA draft DAP implementation guidance, which was intended to satisfy that statutory requirement, was removed from the FDA website in January 2025 following a presidential executive order on DEI programs [19]. As of publication, no final DAP implementation guidance has been issued; the statutory mandate remains in force, but sponsors should distinguish the FDORA statutory framework from currently operative FDA guidance, and verify current DAP submission obligations with regulatory counsel rather than relying on this article alone [23].

    Separately, on December 15, 2025, FDA finalized its guidance on "Enhancing Participation in Clinical Trials: Eligibility Criteria, Enrollment Practices, and Trial Designs" [18]. This guidance is not the final DAP implementation document; it addresses how sponsors should design eligibility criteria and enrollment strategies to include representative populations. Like most FDA guidance, it is not legally binding but reflects the agency's current expectations for well-conducted trials. It covers demographic characteristics (age, sex, race, ethnicity, location of residency) and non-demographic ones (comorbidities, organ dysfunction, disability) and recommends that sponsors eliminate or substantially modify overly restrictive Phase 2 exclusion criteria for subsequent Phase 3 studies [18].

    For Alzheimer's trials specifically, both frameworks point in the same direction: a trial that enrolls predominantly from a narrow demographic and geographic band will face questions about generalizability at review, and those questions become more pointed when the approved therapy is intended for populations the trial did not adequately study. Regardless of the current status of DAP final guidance, the scientific rationale for representative enrollment has not changed.

    A Data-Driven Approach to Alzheimer's Site Selection

    The National Institute on Aging's Alzheimer's Clinical Trials Consortium (ACTC), a cooperative agreement between NIA and a consortium led by USC, Harvard-affiliated hospitals, and Mayo Clinic, established infrastructure at 35 sites across 24 states with an explicit mandate to improve diversity and accelerate startup for Alzheimer's trials [20]. As part of this infrastructure, the ACTC developed a centralized prescreening database (DART) within the AHEAD 3-45 study, collecting zip code, recruitment source, race, ethnicity, and prescreening eligibility status data to systematically understand where participants were entering and exiting the enrollment funnel before study activation [21].

    That kind of geographic and demographic prescreening intelligence, applied before a site is activated rather than after, is the shift that operational teams increasingly need to make. Trade coverage of a Novartis pilot program presented at DPHARM 2024 described an AI-driven diversity-recruitment scoring model in which principal investigators identified as high-diversity recruiters enrolled 2.7 times more targeted Black or African American patients than peers in a large U.S. trial [22]. This is conference presentation coverage and has not been independently peer-reviewed, but the general principle, that PI diversity performance history is measurable and predictive of future diverse enrollment, is consistent with the broader literature on site selection variables.

    The variable driving the Novartis difference was not simply geographic proximity to a diverse neighborhood, but documented PI history of proactive minority outreach. That kind of signal is visible in prior trial data and is the type of insight that structured feasibility analysis can surface before site commitments are made.

    What Alzheimer's site feasibility should measure before activation

    Disease burden vs. diagnostic density
    Claims-based ADRD prevalence compared with estimated true burden by catchment ZIP code
    Demographics and biomarker risk
    Race, ethnicity, age, comorbidity patterns, and published amyloid eligibility risk
    Imaging access
    Amyloid PET availability, distance, mobile imaging options, and regional hospital partnerships
    PI diversity recruitment history
    Prior trial records showing actual minority participant enrollment, not stated intent
    Referral network depth
    Primary care, federally qualified health centers, memory clinics, and community organizations
    Screen-failure risk profile
    Comorbidity and medication exclusions mapped against local population characteristics

    Alzheimer's feasibility should combine burden, access, biomarker, referral, and PI performance signals before sites are selected.

    What Sponsors Should Assess Before Site Activation

    For Alzheimer's trials specifically, a structured pre-activation feasibility assessment should go beyond PI publication lists and existing sponsor relationships. The table below outlines the variables that most directly predict enrollment performance in a high-screen-failure, biomarker-confirmation indication.

    VariableWhat to AssessWhy It Matters for AD Trials
    Disease burden and diagnostic densityClaims-based ADRD prevalence vs. estimated true burden in the catchment ZIP codesLarge gaps suggest undiagnosed populations reachable by outreach but not passive referral
    Population demographics and amyloid eligibility riskRacial and ethnic composition mapped to published amyloid positivity rates by groupSites serving predominantly Black or Hispanic patients should anticipate higher biomarker screen failure rates [16]
    Imaging infrastructure and logisticsDistance from the nearest amyloid PET-capable imaging center; availability of mobile PET partnershipsTransportation burden is a documented barrier; rural sites may require imaging partner agreements before activation
    PI diversity recruitment historyPrior trial records showing enrollment of minority participantsDocumented track record is more predictive than stated intent [22]
    Referral network depthRelationships with primary care, federally qualified health centers, community organizationsAcademic center referrals alone will not produce a diverse cohort
    Screen-failure risk profilingPrevalence of comorbidities (hypertension, diabetes, cardiovascular history) in the catchment population mapped to common AD trial exclusion criteriaDemographically high-risk populations for comorbidities face higher exclusion rates unless protocol criteria are reviewed upstream

    How Kitsa Supports Geographic Intelligence in Site Selection

    KScout, Kitsa's site selection and research site intelligence product, is designed to support this kind of structured feasibility analysis. Rather than relying on historical sponsor relationships or proximity to academic centers as proxies for site quality, KScout is built to surface the demographic, geographic, and operational factors that predict whether a site can enroll the right patients for a given protocol. For Alzheimer's trials, that means layering disease burden data, prior PI performance history, imaging access, and catchment area demographics to identify where enrollment potential and population representativeness align, and where geographic access for underserved communities is built into selection criteria from the outset.

    KScout · Alzheimer's Site Selection Intelligence

    Alzheimer's site selection requires more than academic site history. Sponsors need to understand disease burden, diagnostic gaps, catchment demographics, biomarker screen-failure risk, imaging access, referral networks, and prior PI diversity performance before activation. KScout is designed to surface these feasibility signals so sponsors and CROs can identify sites where enrollment potential and population representativeness align. KScreener can support patient pre-screening workflows where structured eligibility and EHR-connected matching are available.

    Key Takeaways

    • An estimated 7.4 million Americans age 65 and older are living with Alzheimer's dementia in 2026, with Black and Hispanic older adults facing approximately 2x and 1.5x the risk of White Americans respectively, yet these groups account for a small fraction of clinical trial enrollment [1, 2].
    • A 2025 medRxiv preprint covering 88 U.S.-based Phase III Alzheimer's trials from 1997 to 2023 found that nearly half did not report participant race or ethnicity, and fewer than 5% conducted any subgroup analysis by demographic group [2]. These findings are preprint-stage and await peer review, but align directionally with prior peer-reviewed evidence [9].
    • Rural communities show higher Alzheimer's disease burden in cognitive assessment data than their claims-based diagnosed prevalence rates reflect, because diagnostic access is structurally limited; geospatial analysis of Maryland found high ADRD mortality zones in areas with low hospital accessibility [5, 6, 13].
    • Only 11.6% of disease-modifying therapy trials in Alzheimer's and related dementias have been conducted in emerging economies, despite LMICs projected to bear 65% of the global economic burden of ADRD by 2050 [3, 4].
    • Plasma amyloid eligibility data from 4,905 AHEAD 3-45 study participants found that Black and Hispanic participants were less likely to meet amyloid thresholds for trial continuation, a pattern that may reflect population differences in amyloid accumulation and raises questions about threshold generalizability [16].
    • FDORA Section 3601 created the statutory framework for Diversity Action Plans, but applicability is tied to final DAP implementation guidance that has not yet been issued; the January 2025 removal of FDA's draft DAP guidance did not repeal the statute. The FDA's December 2025 final guidance on clinical trial participation addresses eligibility and enrollment design and is the operative agency guidance on those topics [18, 19, 23].
    • Data-driven site selection that accounts for PI recruitment history, catchment demographics, biomarker eligibility risk, and community health infrastructure offers a more systematic alternative to academic-relationship-based site placement, though peer-reviewed validation of specific AI-driven approaches in Alzheimer's site selection remains limited [22].

    References

    1. [1]Alzheimer's Association. "2026 Alzheimer's Disease Facts and Figures." Alzheimer's & Dementia. 2026;22:e71345. https://doi.org/10.1002/alz.71345
    2. [2]Vu T, et al. "Racial and Ethnic Reporting and Representation in Phase III Alzheimer's Disease Clinical Trials in the US, 1997-2023." medRxiv preprint, May 2025. [Preprint; not yet peer-reviewed] https://doi.org/10.1101/2025.05.03.25326933
    3. [3]Llibre-Guerra JJ, et al. "A Call for Clinical Trial Globalization in Alzheimer's Disease and Related Dementia." Alzheimer's & Dementia. February 2023. https://doi.org/10.1002/alz.12995
    4. [4]Bartsch P, et al. "Global and Regional Projections of the Economic Burden of Alzheimer's Disease and Related Dementias from 2019 to 2050: A Value of Statistical Life Approach." eClinicalMedicine (The Lancet). July 2022. https://doi.org/10.1016/j.eclinm.2022.101580
    5. [5]Gilmore-Bykovskyi A, et al. "Rural-Urban Differences in Diagnostic Incidence and Prevalence of Alzheimer's Disease and Related Dementias." PubMed Central, 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8277695/
    6. [6]Kramer DB, et al. "Rural-Urban Disparities of Alzheimer's Disease and Related Dementias: A Scoping Review." Alzheimer's & Dementia: Translational Research & Clinical Interventions. February 2025. https://doi.org/10.1002/trc2.70047
    7. [7]Boehme AK, et al. "Advancing the Science of Recruitment for Alzheimer's Clinical Trials: Challenges and Opportunities." Journal of Prevention of Alzheimer's Disease. 2025. [Review article summarizing a 2024 USC cross-sector roundtable; enrollment pipeline figures reflect expert consensus estimates from 40 participants; primary sources include Rafii et al. and U.S. Alzheimer's Clinical Trials Landscape analyses] https://pmc.ncbi.nlm.nih.gov/articles/PMC12321627/
    8. [8]ACRP. "Alzheimer's Trials: Challenges, Determination, and the People Behind Progress." ACRP, September 2025. [Trade synthesis; primary sources cited include Mitchell et al. 2024 and Clement et al. 2019 for the 10-27% eligibility estimate] https://acrpnet.org/2025/09/02/alzheimers-trials-challenges-determination-and-the-people-behind-progress
    9. [9]Manly JJ, et al. "Disparities by Race and Ethnicity Among Adults Recruited for a Preclinical Alzheimer Disease Trial." JAMA Network Open. 2021;4(7):e2114605. https://pmc.ncbi.nlm.nih.gov/articles/PMC8261604/
    10. [10]Showell S, Murphy J, Dent G, Dawson K. "Advancing Inclusivity for African American and Hispanic Populations in Alzheimer's Disease Trials: Understanding Screen Failures from the Aducanumab Confirmatory Trial." Alzheimer's & Dementia, conference abstract, January 2025. [Conference-level evidence; findings are preliminary] https://pmc.ncbi.nlm.nih.gov/articles/PMC11713872/
    11. [11]Doody RS, et al. "The Current State of the Screening and Enrollment Pipeline for Clinical Research Engagement in the Era of Disease Modifying Therapies for Alzheimer's Disease." Alzheimer's & Dementia, conference abstract, 2025. [Single-site experience reported at conference; findings should not be generalized without caution] https://pmc.ncbi.nlm.nih.gov/articles/PMC12741756/
    12. [12]SiteRx. "SiteRx AI-Enabled Clinical Intelligence Platform Delivers Superior Amyloid PET Conversion in Early Alzheimer's Disease Trial." Alzheimer's & Dementia, conference abstract, January 2025. [Vendor-authored conference abstract; independent peer-reviewed validation not published] https://pmc.ncbi.nlm.nih.gov/articles/PMC11713331/
    13. [13]Namadi SS, et al. "Access to Hospitals for People with Alzheimer's Disease and Related Dementias." Journal of Transport & Health. 2026. https://doi.org/10.1016/j.jth.2026.102304
    14. [14]Ferdows N. "Rural-Urban Disparities in Alzheimer's Disease and Related Dementia: The Role of State-Level Nurse Practitioner Policies." Alzheimer's & Dementia, conference abstract (Gerontological Society of America annual meeting supplement), December 2024. [Conference abstract; directional findings consistent with broader Medicare claims literature] https://pmc.ncbi.nlm.nih.gov/articles/PMC12724791/
    15. [15]Cummings JL, et al. "Alzheimer's Disease Progression by Geographical Region in a Clinical Trial Setting." Alzheimer's Research & Therapy. 2015. https://pmc.ncbi.nlm.nih.gov/articles/PMC4481070/
    16. [16]Molina-Henry DP, Raman R, Liu A, et al. "Racial and Ethnic Differences in Plasma Biomarker Eligibility for a Preclinical Alzheimer's Disease Trial." Alzheimer's & Dementia. 2024;20:3827-3838. https://doi.org/10.1002/alz.13803
    17. [17]Esquivel RN, Mathur S, Parker C, et al. "Blood-Based Biomarkers Enrich for Amyloid Positive Participants, Reducing Patient Burden in PROGRESS-AD." Alzheimer's & Dementia, conference abstract, December 2025. [Phase 2 trial; conference-level evidence; findings are preliminary] https://pmc.ncbi.nlm.nih.gov/articles/PMC12741176/
    18. [18]U.S. Food and Drug Administration. "Enhancing Participation in Clinical Trials: Eligibility Criteria, Enrollment Practices, and Trial Designs." Guidance for Industry, December 15, 2025. [Final guidance superseding the November 2020 draft on the same subject; separate from FDORA's statutory Diversity Action Plan requirements under Pub. L. 117-328] https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enhancing-participation-clinical-trials-eligibility-criteria-enrollment-practices-and-trial-designs
    19. [19]AJMC. "FDA Quietly Removes Draft Guidance on Diversity in Clinical Trials Following Executive Order on DEI." AJMC, January 2025. https://www.ajmc.com/view/fda-quietly-removes-draft-guidance-on-diversity-in-clinical-trials-following-executive-order-on-dei
    20. [20]National Institute on Aging. "Alzheimer's Clinical Trials Consortium (ACTC)." NIA, NIH. https://www.nia.nih.gov/research/dn/alzheimers-clinical-trials-consortium-actc
    21. [21]Grill JD, et al. "Centralizing Prescreening Data Collection to Inform Data-Driven Approaches to Clinical Trial Recruitment." Contemporary Clinical Trials, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10152012/
    22. [22]Clinical Trial Vanguard. "How Novartis Is Using AI for Clinical Trial Feasibility and Site Selection." December 2024. [Trade/conference coverage; not peer-reviewed; independent validation not published] https://www.clinicaltrialvanguard.com/conference-coverage/how-novartis-is-using-ai-for-clinical-trial-feasibility-and-site-selection/
    23. [23]Food and Drug Omnibus Reform Act of 2022, Pub. L. No. 117-328, Section 3601, Consolidated Appropriations Act, 2023 (Dec. 29, 2022). [Statutory text; Section 3601 mandates Diversity Action Plan submission for pivotal clinical studies of drugs and devices] https://www.congress.gov/117/bills/hr2617/BILLS-117hr2617enr.pdf

    FAQ

    Frequently asked questions

    Why do Alzheimer's clinical trials enroll mostly from academic medical centers?
    Academic medical centers have the infrastructure genuinely required for Alzheimer's trials: neuroimaging, trained coordinators, research pharmacy, established IRB systems, and specialty nursing. For studies requiring amyloid PET confirmation and cognitive assessments over 18 months or longer, these capabilities are real prerequisites. The problem is not that academic sites are selected, but that site selection has rarely extended beyond them even when the patient populations needed are elsewhere. Community health centers and federally qualified health centers serving minority communities, and sites in rural high-burden areas, can be developed if sponsors begin site qualification earlier and invest in building capacity, including mobile phlebotomy, imaging partnerships, and transport programs, rather than relying on established academic rosters.
    What is the relationship between geographic site placement and screen failure rates?
    Screen failure rates in Alzheimer's trials range from roughly 74% to above 90% depending on the population [10, 11]. Sites placed near communities with high rates of undertreated cardiovascular comorbidities, which disproportionately affect minority populations, will encounter more exclusionary comorbidity failures. Sites far from imaging facilities shift screening logistics onto participants, increasing dropout before eligibility is confirmed. Geographic site selection that accounts for comorbidity burden, transportation access, and biomarker eligibility patterns is operationally linked to enrollment efficiency, though the precise magnitude of this relationship has not been quantified in peer-reviewed controlled comparisons.
    What does the FDA currently require regarding diversity in trial site selection?
    FDORA Section 3601, enacted in 2022, created the statutory framework for Diversity Action Plan submission for pivotal clinical studies [23]. The statute ties applicability to enrollment commencement 180 days after publication of final DAP implementation guidance. The June 2024 draft DAP guidance intended to fulfill that requirement was removed from the FDA website in January 2025 [19]; no final DAP implementation guidance has been issued as of publication. The FDORA statutory mandate has not been repealed, but sponsors should confirm current DAP submission obligations with regulatory counsel. Separately, the FDA's December 2025 final guidance on "Enhancing Participation in Clinical Trials" addresses eligibility criteria and enrollment practices and is the current operative FDA guidance on trial representativeness [18]; it is not the final DAP implementation document.
    How does Alzheimer's prevalence differ between rural and urban areas?
    The data present a consistent pattern: Medicare claims data show lower diagnosed ADRD prevalence in rural counties, while cognitive assessment data from survey-based studies show higher prevalence in rural areas [14]. The leading interpretation is that rural areas have higher true disease burden but lower diagnostic capture, meaning rural patients are more likely to die without a formal diagnosis and therefore without ever being referred to a clinical trial [5, 6]. A 2026 geospatial study of Maryland found high ADRD mortality rates in rural eastern and southern counties paired with low diagnosis rates at the same locations, a pattern consistent with systematic underdiagnosis rather than lower underlying risk [13].
    Can AI improve site selection for Alzheimer's trials?
    Available early-stage evidence suggests AI can support more systematic site selection by analyzing PI recruitment history, characterizing catchment area demographics, and identifying geographic regions where disease burden and patient accessibility align. A Novartis pilot described in trade coverage from DPHARM 2024 showed that AI-identified high-diversity PIs enrolled 2.7 times more targeted minority participants than matched peers, though this finding has not been independently peer-reviewed [22]. An AI-driven prescreening platform reported a 64% amyloid PET pass rate versus 23% from conventional sources in a vendor-authored conference abstract [12]. Both data points are preliminary; these tools are most useful as decision-support inputs to feasibility analysis rather than as replacements for structured site assessment.
    Why are clinical trial sites so concentrated in specific geographic regions?
    Site concentration reflects compounding factors: historical sponsor relationships with established PIs, the genuine infrastructure requirements of complex trials, regulatory familiarity at sites with prior study experience, and lower perceived operational risk from working with known institutions. These are real operational considerations. The consequence is that the map of Alzheimer's trial sites closely follows the map of academic neurology rather than the map of Alzheimer's disease burden, and those two maps are substantially different at both the national and global levels.