{
  "slug": "amyloid-cascade",
  "title": "Amyloid-beta as the Primary Upstream Cause of Alzheimer's Disease",
  "claim": "Accumulation of amyloid-β is the primary upstream cause of Alzheimer's disease: it initiates the disease process and causally drives the tau pathology and neurodegeneration that follow, across the disease class.",
  "update_date": "2026-10-05",
  "search_cutoff": "2026-10-05",
  "framework_for_addendum": "HSEF v5.3 causal distinctions",
  "historical_scorecard_schema": "5.4",
  "regraded": false,
  "status": "curated_local_addendum",
  "full_academic_review_complete": false,
  "summary": "Genetics, biomarker ordering and treatment trials support an upstream amyloid contribution in defined settings. Benefit after plaque removal varies across trials, and a universal amyloid-to-tau-to-neurodegeneration chain remains a separate question.",
  "timeline": [
    {
      "year": "1991",
      "source_id": "P1671712",
      "design": "Familial segregation",
      "finding": "APP missense variation segregated with familial Alzheimer disease.",
      "limit": "A specific inherited route does not establish the initiating cause of all sporadic disease.",
      "historical_anchor_only": false
    },
    {
      "year": "2005",
      "source_id": "P16369530",
      "design": "Familial copy-number study",
      "finding": "APP duplication was identified in families with early-onset disease and cerebral amyloid angiopathy.",
      "limit": "The duplicated locus and inherited exposure differ from ordinary sporadic disease.",
      "historical_anchor_only": false
    },
    {
      "year": "2007",
      "source_id": "P17478722",
      "design": "Mouse tau reduction",
      "finding": "Reducing tau prevented deficits despite persistently high amyloid.",
      "limit": "A model-specific downstream dependency does not establish the human mediation chain.",
      "historical_anchor_only": false
    },
    {
      "year": "2012",
      "source_id": "P22784036",
      "design": "DIAN baseline biomarker study",
      "finding": "Biomarker abnormalities were ordered relative to expected inherited-disease onset.",
      "limit": "The authors called for longitudinal confirmation; chronology is not a causal perturbation.",
      "historical_anchor_only": false
    },
    {
      "year": "2012",
      "source_id": "P22801501",
      "design": "Human genetics plus cell assay",
      "finding": "APP A673T was associated with protection and reduced amyloidogenic peptide formation in vitro.",
      "limit": "Rare lifelong genetic exposure is not equivalent to late-life plaque removal.",
      "historical_anchor_only": false
    },
    {
      "year": "2019",
      "source_id": "P31686034",
      "design": "Single protective-genotype case",
      "finding": "An APOE3 Christchurch homozygote had delayed impairment despite extensive amyloid.",
      "limit": "A single case bounds simple sufficiency but cannot estimate prevalence.",
      "historical_anchor_only": false
    },
    {
      "year": "2022",
      "source_id": "P36449413",
      "design": "Clarity AD randomized trial",
      "finding": "Lecanemab modestly slowed decline over 18 months, with adverse events.",
      "limit": "Treatment contribution does not establish disease initiation or complete tau mediation.",
      "historical_anchor_only": false
    },
    {
      "year": "2023",
      "source_id": "P37459141",
      "design": "TRAILBLAZER-ALZ 2 randomized trial",
      "finding": "Donanemab slowed progression in the prespecified symptomatic trial populations.",
      "limit": "Selected amyloid/tau-positive participants and treatment harms bound generalization.",
      "historical_anchor_only": false
    },
    {
      "year": "2023",
      "source_id": "P37966285",
      "design": "GRADUATE I and II randomized trials",
      "finding": "Gantenerumab reduced plaques without significant benefit on either trial’s primary clinical endpoint.",
      "limit": "Incomplete clearance and exposure duration limit a universal negative interpretation; two trials are one report.",
      "historical_anchor_only": false
    },
    {
      "year": "2024",
      "source_id": "P38381674",
      "design": "Sporadic nested case-control follow-up",
      "finding": "Amyloid-related biomarkers diverged before other markers and cognitive decline.",
      "limit": "Observed ordering does not isolate a necessary cause.",
      "historical_anchor_only": false
    },
    {
      "year": "2025",
      "source_id": "P40120616",
      "design": "DIAN-TU open-label extension",
      "finding": "Long exposure suggested possible delay, while short or partial removal lacked significant clinical effects.",
      "limit": "External controls and extension selection prevent treating this as a fresh randomized prevention result.",
      "historical_anchor_only": false
    }
  ],
  "gaps": [
    {
      "id": "G1",
      "question": "Does early amyloid removal prevent sporadic clinical onset?",
      "source_ids": [
        "P36449413",
        "P37459141",
        "P38381674",
        "P40120616"
      ],
      "alternative": "Late symptomatic benefit may reflect contribution after initiation, while tau or other injury becomes self-sustaining.",
      "discriminating_test": "Long-duration prevention randomization in biomarker-defined presymptomatic groups; prespecify clinical onset, clearance, tau trajectory and adverse events.",
      "gap_type": "bounded_causal_uncertainty",
      "interpretation": "An unresolved inference or scope limit in the checked evidence, not a claim that no relevant study exists anywhere."
    },
    {
      "id": "G2",
      "question": "Does tau change mediate clinical benefit?",
      "source_ids": [
        "P17478722",
        "P37459141",
        "P37966285"
      ],
      "alternative": "Amyloid and tau biomarkers can move together without tau carrying the treatment effect.",
      "discriminating_test": "Repeated tau PET and neurodegeneration measures within randomization; specify mediator timing, missingness and sensitivity to mediator–outcome confounding.",
      "gap_type": "bounded_causal_uncertainty",
      "interpretation": "An unresolved inference or scope limit in the checked evidence, not a claim that no relevant study exists anywhere."
    },
    {
      "id": "G3",
      "question": "Which clearance, species and exposure matter?",
      "source_ids": [
        "P36449413",
        "P37459141",
        "P37966285",
        "P40120616"
      ],
      "alternative": "Differences may arise from drug kinetics, target species, dose, disease stage or incomplete clearance.",
      "discriminating_test": "Harmonized analyses and prospectively matched trials with target engagement, baseline tau and equivalent outcome schedules; avoid cross-trial causal attribution.",
      "gap_type": "bounded_causal_uncertainty",
      "interpretation": "An unresolved inference or scope limit in the checked evidence, not a claim that no relevant study exists anywhere."
    },
    {
      "id": "G4",
      "question": "Where does amyloid fail to be sufficient?",
      "source_ids": [
        "P1671712",
        "P16369530",
        "P31686034"
      ],
      "alternative": "Protective host factors may block downstream tau pathology despite high amyloid.",
      "discriminating_test": "Genotype-stratified longitudinal cohorts and mechanistic follow-up with independent protective cases; retain disease subtype boundaries.",
      "gap_type": "bounded_causal_uncertainty",
      "interpretation": "An unresolved inference or scope limit in the checked evidence, not a claim that no relevant study exists anywhere."
    }
  ],
  "source_cards": [
    {
      "id": "P1671712",
      "pmid": "1671712",
      "doi": "10.1038/349704a0",
      "title": "Segregation of a missense mutation in the amyloid precursor protein gene with familial Alzheimer's disease.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/1671712/",
      "issue_year": "1991",
      "electronic_date": "",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Research Support, Non-U.S. Gov't",
        "Research Support, U.S. Gov't, P.H.S."
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P16369530",
      "pmid": "16369530",
      "doi": "10.1038/ng1718",
      "title": "APP locus duplication causes autosomal dominant early-onset Alzheimer disease with cerebral amyloid angiopathy.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/16369530/",
      "issue_year": "2006",
      "electronic_date": "2005-12-20",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Research Support, Non-U.S. Gov't"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P17478722",
      "pmid": "17478722",
      "doi": "10.1126/science.1141736",
      "title": "Reducing endogenous tau ameliorates amyloid beta-induced deficits in an Alzheimer's disease mouse model.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/17478722/",
      "issue_year": "2007",
      "electronic_date": "",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Research Support, N.I.H., Extramural",
        "Research Support, Non-U.S. Gov't"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P22801501",
      "pmid": "22801501",
      "doi": "10.1038/nature11283",
      "title": "A mutation in APP protects against Alzheimer's disease and age-related cognitive decline.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/22801501/",
      "issue_year": "2012",
      "electronic_date": "",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Research Support, N.I.H., Extramural"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P22784036",
      "pmid": "22784036",
      "doi": "10.1056/NEJMoa1202753",
      "title": "Clinical and biomarker changes in dominantly inherited Alzheimer's disease.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/22784036/",
      "issue_year": "2012",
      "electronic_date": "2012-07-11",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Research Support, N.I.H., Extramural",
        "Research Support, Non-U.S. Gov't"
      ],
      "correction_notices": [
        {
          "type": "ErratumIn",
          "pmid": "",
          "note": ""
        }
      ],
      "cohort_note": "DIAN observational cohort; separate from randomized DIAN-TU but overlapping disease network.",
      "baseline_access_depth": "full_text_partial",
      "complete_paper_examined_in_this_update": false,
      "notice_check_scope": "Linked notice presence was checked in the primary record; its scientific impact was not verified in this update."
    },
    {
      "id": "P31686034",
      "pmid": "31686034",
      "doi": "10.1038/s41591-019-0611-3",
      "title": "Resistance to autosomal dominant Alzheimer's disease in an APOE3 Christchurch homozygote: a case report.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/31686034/",
      "issue_year": "2019",
      "electronic_date": "2019-11-04",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Case Reports",
        "Journal Article",
        "Research Support, N.I.H., Extramural",
        "Research Support, Non-U.S. Gov't"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "full_text_partial",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P36449413",
      "pmid": "36449413",
      "doi": "10.1056/NEJMoa2212948",
      "title": "Lecanemab in Early Alzheimer's Disease.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/36449413/",
      "issue_year": "2023",
      "electronic_date": "2022-11-29",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Clinical Trial, Phase III",
        "Journal Article",
        "Multicenter Study",
        "Randomized Controlled Trial",
        "Research Support, Non-U.S. Gov't"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P37459141",
      "pmid": "37459141",
      "doi": "10.1001/jama.2023.13239",
      "title": "Donanemab in Early Symptomatic Alzheimer Disease: The TRAILBLAZER-ALZ 2 Randomized Clinical Trial.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/37459141/",
      "issue_year": "2023",
      "electronic_date": "",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Research Support, Non-U.S. Gov't"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "full_text_partial",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P37966285",
      "pmid": "37966285",
      "doi": "10.1056/NEJMoa2304430",
      "title": "Two Phase 3 Trials of Gantenerumab in Early Alzheimer's Disease.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/37966285/",
      "issue_year": "2023",
      "electronic_date": "",
      "access_depth": "full_text_partial",
      "checked_details": "Results P25/P28: both trial-specific primary CDR-SB tests were nonsignificant; only a minority attained amyloid-negative status. Pooled/exploratory results are not replacements for the primary tests.",
      "publication_types": [
        "Randomized Controlled Trial",
        "Clinical Trial, Phase III",
        "Journal Article",
        "Research Support, N.I.H., Extramural"
      ],
      "correction_notices": [],
      "cohort_note": "Two GRADUATE trial cohorts within one publication; one timeline entry.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P38381674",
      "pmid": "38381674",
      "doi": "10.1056/NEJMoa2310168",
      "title": "Biomarker Changes during 20 Years Preceding Alzheimer's Disease.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/38381674/",
      "issue_year": "2024",
      "electronic_date": "",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Multicenter Study",
        "Research Support, Non-U.S. Gov't",
        "Research Support, N.I.H., Extramural",
        "Observational Study"
      ],
      "correction_notices": [],
      "cohort_note": "No independence claim made; cohort identity beyond the cited report was not exhaustively audited.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false
    },
    {
      "id": "P40120616",
      "pmid": "40120616",
      "doi": "10.1016/S1474-4422(25)00024-9",
      "title": "Safety and efficacy of long-term gantenerumab treatment in dominantly inherited Alzheimer's disease: an open-label extension of the phase 2/3 multicentre, randomised, double-blind, placebo-controlled platform DIAN-TU trial.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/40120616/",
      "issue_year": "2025",
      "electronic_date": "",
      "access_depth": "abstract_excerpt_checked",
      "checked_details": "Primary record and selected abstract passages checked; no complete-paper appraisal credited.",
      "publication_types": [
        "Journal Article",
        "Randomized Controlled Trial",
        "Multicenter Study",
        "Clinical Trial, Phase III",
        "Clinical Trial, Phase II"
      ],
      "correction_notices": [
        {
          "type": "ErratumIn",
          "pmid": "40651485",
          "note": ""
        }
      ],
      "cohort_note": "DIAN-TU extension: continuation of the prior trial, not an independent randomized replication.",
      "baseline_access_depth": "abstract_metadata",
      "complete_paper_examined_in_this_update": false,
      "notice_check_scope": "Linked notice presence was checked in the primary record; its scientific impact was not verified in this update."
    }
  ],
  "access_counts": {
    "full_text_partial": 1,
    "abstract_excerpt_checked": 10,
    "metadata_only": 0
  },
  "browser_messages": 3,
  "targeted_check": {
    "pmid": "37966285",
    "provider_access": "selected primary full-text passages reported by Consensus",
    "independent_primary_body_crosscheck": true,
    "verification_scope": "Results P25/P28: both trial-specific primary CDR-SB tests were nonsignificant; only a minority attained amyloid-negative status. Pooled/exploratory results are not replacements for the primary tests."
  },
  "editorial_warning": "The first Pro timeline duplicated four reports into ten entries. It was replaced after a Deep follow-up and primary-record checks. Retracted Lesné 2006 is excluded from positive evidence.",
  "reading_limit": "This focused addendum does not establish 50–70 complete primary Methods/Results examinations per review. Baseline reading receipts and scores retain their original scope.",
  "method": "Case-specific Consensus records assisted gap discovery, chronology and targeted paper questions. Shared template wording about an amyloid-specific Deep follow-up is not evidence of a Deep run for this topic; the dated source records establish the actual use and access limits. Primary identifiers, selected abstract passages, correction notices and available primary-body passages were cross-checked. Generated absence cells, duplicate milestones and unsupported access claims were rejected."
}