Eight observational studies were selected, carried out in humans and, therefore, suitable for inclusion in this review. 3 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
Research
27,780 Alzheimer's and dementia studies in plain English, each scored out of 100.
Of 4,150 studies screened, 26 were eligible for inclusion, of which 17 were human studies, 8 were preclinical animal studies, and 1 included both human and preclinical animal studies. 4 key findings →
Design: narrative review Participants: 12 Evidence: low
Full summary, score breakdown and related studies → Original source Free full text
Alzheimer's disease (AD) is a progressive neurodegenerative condition representing the most common cause of dementia and currently affects millions of people worldwide. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source Free full text
Alzheimer's disease (AD) was used to describe pre-senile dementia to differentiate it from senile dementia, which develops in the adult age group of more than 65 years. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
The highest density of microbes resides in human gastrointestinal tract, known as "Gut microbiome". 3 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
Gut microbiota is emerging as a key regulator of many disease conditions and its dysregulation is implicated in the pathogenesis of several gastrointestinal and extraintestinal disorders. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
The human oral microbiome can affect brain functions directly through the trigeminal nerve and olfactory system and indirectly via the oral-gut-brain axis. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
41/100
Understanding how gut flora influences gut-brain communications has been the subject of significant research over the past decade. 3 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
The composition of the gut microbiota influences the CNS, resulting in changes in host behavior and may be related to the development of neurodegenerative diseases. 4 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
The microbiota-gut-brain axis refers to the intricate bidirectional communication between commensal microorganisms residing in the digestive tract and the central nervous system, along neuroendocrine, metabolic, immune, and inflammatory pathways. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
Alzheimer's disease (AD) and related dementias (ADRD) are still a serious global public health concern more than a century after the German neuropathologist and psychiatrist Dr. Aloysius Alzheimer described the first case. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
Neurodegenerative diseases comprise a diverse group of progressive disorders characterized by the selective and irreversible loss of neuronal structure and function within the specific regions of the central and/or peripheral nervous systems. 5 key findings →
Design: narrative review Evidence: low
Full summary, score breakdown and related studies → Original source
Where “Free full text” comes from
Free full text links and the Full text may need a subscription label come from Unpaywall, Europe PMC and OpenAlex records of free copies, checked 10 Oct 2026. A study with neither is unknown, not paywalled. Show only studies that are free to read
How the 0–100 score works — and why some entries are capped
This is alzhub's own score. It is not an official metric, not an impact factor, and no journal, publisher or ranking body endorses it. We built it so that a reader who is not a scientist can tell a landmark trial from a conference abstract without having to already know the difference. Every point comes from one of 20 components, all of them printed on the study itself, so you can disagree with our arithmetic rather than having to trust the total.
- Journal tier up to 10 pts
- Journal's citation record up to 4 pts
- Study design up to 12 pts
- Strength of evidence up to 5 pts
- Peer-review validation up to 10 pts
- How recent up to 5 pts
- Sample size up to 4 pts
- Effect reported up to 3 pts
- Studied in people up to 3 pts
- Randomised / blinded up to 2 pts
- Times cited up to 7 pts
- Citations per year up to 5 pts
- Impact for its field and year up to 6 pts
- Cited by studies here up to 6 pts
- Still being cited up to 4 pts
- Senior author's track record up to 4 pts
- Institution's track record up to 3 pts
- Multi-centre collaboration up to 3 pts
- Indexed in PubMed up to 2 pts
- Free to read up to 2 pts
Journals are placed in ordered tiers, never given a numeric impact factor — we could not verify current impact factors from a source we control, and an invented one would be worse than none. Tier 1 is the top-tier general journals (NEJM, The Lancet, JAMA, Nature, Science, Nature Medicine); tier 2 is the leading specialty journals; tier 3 is every other peer-reviewed journal. A separate part scores how much the journal's own papers are cited, which tells the tier-3 journals apart.
Two rules we don't bend. First, we never fill in a missing value: if a record does not state a sample size or a design, that component scores zero, and if we simply have no data for a part, such as a citation count, that part is left out and the study is scored on the parts we could check. The study card says which. Second, anything that is not a peer-reviewed article is capped at 16/100 and carries a warning chip — so a conference abstract or a company press release can never outrank a peer-reviewed paper, no matter how good it looks.
We rank a rigorous null result — a good trial showing that something does not work — above an early positive finding. Someone deciding whether to buy a supplement is served by that, and the rigour is already counted by the design and journal components.
The score is computed from the published data alone and is reproducible: the same file always yields the same numbers.
See the whole rubric drawn out → — four charts covering all 27,780 studies: how the scores are spread and where the cap bites, which of the 20 components the library is strong and weak on, which subjects rest on stronger evidence, and what kinds of study each subject is actually built from.
What this library is — and isn't
This is a large sample of the Alzheimer's literature, not an exhaustive index of it. It holds 27,780 records, built mostly from automated pulls of Europe PMC (61.1% of the library) and OpenAlex (18.3%), plus smaller pulls from PubMed, Crossref and medRxiv. If a study, a drug, or a finding isn't here, that is not evidence it doesn't exist in the literature — it may simply not have been pulled in yet.
1,034 records (3.7% of the library) are not peer-reviewed — 962 of those are preprints posted before any journal review, and the rest are conference abstracts, regulatory notices and reports. Every study card on this page states its status plainly, and the score above is capped for anything that isn't a peer-reviewed article.
See the full, machine-readable breakdown of this library's coverage →