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Finding the falsification threshold of the toxic proteinopathy hypothesis in neurodegeneration
Espay AJ, Herrup K, Daly T.. Handbook of clinical neurology, 2023-01-01
Topic: Brain proteins, microglia and lab models
A biomedical hypothesis is a theoretical assumption amenable to being tested in a randomized clinical trial. The main hypotheses in neurodegenerative disorders are based on the concept that proteins accumulate in an aggregated fashion and trigger toxicity. The toxic proteinopathy hypothesis posits that neurodegeneration is caused by toxicity of aggregated amyloid in Alzheimer's disease (toxic amyloid hypothesis), aggregated α-synuclein in Parkinson's disease (toxic synuclein hypothesis), and aggregated tau in progressive supranuclear palsy (toxic tau hypothesis). To date, we have accumulated 40 negative anti-amyloid randomized clinical, 2 anti-synuclein trials, and 4 anti-tau trials. These results have not prompted a major reconsideration of the toxic proteinopathy hypothesis of causality. Imperfections in trial design and execution (incorrect dosage, insensitive endpoints, too-advanced population) but not in the underlying hypotheses have prevailed as explaining the failures. We review here the evidence suggesting that the threshold of hypothesis falsifiability may be too high and advocate in favor of a minimal set of rules that facilitate the interpretation of negative clinical trials as falsifying the driving hypotheses, in particular if the desirable change in surrogate endpoints has been achieved. We propose four steps to refute a hypothesis in future-negative surrogate-backed trials and argue that for the actual rejection to take place, refutation must be accompanied by the proposal of an alternative hypothesis. The absence of alternative hypotheses may be the single greatest reason why there remains hesitancy in rejecting the toxic proteinopathy hypothesis: in the absence of alternatives, we have no clear guidance as to where to redirect or focus.
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APA 7th
Espay, A. J., Herrup, K., & Daly, T. (2023). Finding the falsification threshold of the toxic proteinopathy hypothesis in neurodegeneration. Handbook of clinical neurology. https://doi.org/10.1016/b978-0-323-85538-9.00008-0
Vancouver
Espay AJ, Herrup K, Daly T. Finding the falsification threshold of the toxic proteinopathy hypothesis in neurodegeneration. Handbook of clinical neurology. 2023. doi:10.1016/b978-0-323-85538-9.00008-0. PMID: 36796939.
BibTeX
@article{espay2023-36796939,
author = {Espay, A. J. and Herrup, K. and Daly, T.},
title = {{Finding the falsification threshold of the toxic proteinopathy hypothesis in neurodegeneration}},
journal = {Handbook of clinical neurology},
year = {2023},
doi = {10.1016/b978-0-323-85538-9.00008-0},
pmid = {36796939},
url = {https://doi.org/10.1016/b978-0-323-85538-9.00008-0}
}
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Key findings
- These results have not prompted a major reconsideration of the toxic proteinopathy hypothesis of causality.
- We review here the evidence suggesting that the threshold of hypothesis falsifiability may be too high and advocate in favor of a minimal set of rules that facilitate the interpretation of negative clinical trials as falsifying the driving hypotheses, in particular if the desirable change in surrogate endpoints has been achieved.
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Study details
- Evidence strengthHigh
How this study scored 47/100
Published in a peer-reviewed journal. Scored zero for study design, sample size, effect reported, studied in people and randomised / blinded because the record does not state it. We have no data on journal's citation record, times cited, citations per year, impact for its field and year, cited by studies here, still being cited, senior author's track record, institution's track record and multi-centre collaboration, so those were left out: it earned 27 of the 58 points we could judge it on, which is 47 out of 100.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (Handbook of clinical neurology) |
| Journal's citation record | — / 4 | No journal record from OpenAlex — left out of this score |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 5 / 5 | Rated “high” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 3 / 5 | 2023 — within 6 year(s) of the newest study here |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | — / 7 | No citation count (not found in OpenAlex) — left out of this score |
| Citations per year | — / 5 | No citation count or no year — left out of this score |
| Impact for its field and year | — / 6 | No field-weighted citation impact (OpenAlex has none yet) — left out of this score |
| Cited by studies here | — / 6 | Not yet checked against this library's citation graph — left out of this score |
| Still being cited | — / 4 | No yearly citation counts — left out of this score |
| Senior author's track record | — / 4 | Senior author's record not available — left out of this score |
| Institution's track record | — / 3 | No institution listed in OpenAlex — left out of this score |
| Multi-centre collaboration | — / 3 | Institutions not listed — left out of this score |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 36796939) |
| Free to read | 0 / 2 | Behind a paywall — scores zero |
| Points | 27 / 58 | Scored on 11 of 20 parts. We have no data for the rest, so they are left out: 27 of the 58 points we could judge it on is 47 out of 100. |
| Total | 47 / 100 | — |
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