## Evidence Quality Audit: Amyloid Cascade Hypothesis
**Evidence Score: 0.62/1.0**
### Quality Concerns Identified:
1. **Citation Authenticity Issues**
- **Problem**: 2022 Science investigation revealed potentially manipulated images in influential 2006 Nature paper (Lesné et al.) proposing Aβ*56 oligomers as key toxic species
- **Impact**: ~2,300 citations to potentially compromised work; undermines specific oligomer-toxicity claims
- **Action**: MODIFY - core amyloid hypothesis survives, but specific Aβ*56 mechanism requires re-evaluation
2. **Publication Bias & Selective Reporting**
- **Problem**: Decades of failed anti-amyloid trials (bapineuzumab, solanezumab, gantenerumab Phase III failures) were under-emphasized while positive preclinical data was over-represented
- **Effect Size**: Recent approved drugs (lecanemab, donanemab) show only modest clinical benefit (0.45-0.67 CDR-SB points over 18 months)
- **Action**: MODIFY - hypothesis partially validated but effect sizes much smaller than early literature suggested
3. **Genetic Evidence Consistency**
- **Strength**: APP, PSEN1, PSEN2 mutations causing early-onset AD consistently increase Aβ42 production (>100 families, LOD scores >3.0)
- **Concern**: These represent <5% of AD cases; generalizability to sporadic AD unclear
- **Verdict**: ACCEPT genetic evidence as high-quality support for amyloid's causal role in familial AD
4. **Temporal Relationship Evidence**
- **Strength**: Biomarker studies (DIAN, A4) show amyloid accumulation precedes tau and neurodegeneration by 10-20 years
- **Concern**: Correlation ≠ causation; amyloid could be parallel process rather than upstream trigger
- **Statistical Rigor**: Path analysis models show mixed results on whether amyloid mediates tau spread
5. **Replication Crisis**
- **Problem**: Many foundational rodent studies showing dramatic cognitive rescue with amyloid clearance have failed to replicate in human trials
- **Action**: MODIFY - animal model predictions did not translate
### Overall Verdict: **MODIFY**
The amyloid cascade hypothesis retains importance but requires substantial modification:
**Accept:**
- Amyloid plays *a* causal role (genetic evidence, biomarker trajectories, modest therapeutic efficacy)
- Accumulation is necessary but insufficient for AD in most cases
**Reject:**
- Amyloid as sole or primary driver in sporadic AD
- Magnitude of benefit from amyloid removal as initially predicted
- Specific Aβ*56 oligomer mechanism from compromised 2006 work
**Confidence in Evidence: 0.70**
The hypothesis remains scientifically important as:
1. A validated therapeutic target (albeit with modest effect)
2. Part of a multi-factorial model alongside tau, inflammation, vascular factors
3. A cautionary tale about publication bias and image integrity in high-impact science
Recommendation: Reframe from "cascade" to "contributing factor" in multifactorial neurodegeneration model.