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What you are reading, and what it is not

Every quote on this page is verbatim. It is the sentence as the authors wrote it, pulled from the open-access full text or, where there is none, from the published abstract. Nothing has been reworded or smoothed. Where a quote held citation numbers, they were removed and the gap is shown as [ ]. Quotes taken from an abstract rather than the full discussion are marked abstract only.

A research suggestion is a question the authors raised — not a finding, and not a recommendation. When a paper says a longer trial is needed, that tells you the authors thought the question was open. It does not tell you what the answer will be, and it is not advice about anything you should do.

The theme headings are ours. Grouping hundreds of sentences requires naming the groups, and those names are our summary, not the authors' words. That is the only paraphrase on this page, and the verbatim quote always sits directly underneath its heading so you can check the fit yourself.

Collected 2026-09-24 from the 369 studies in our library. Full text via Europe PMC; abstracts via PubMed.

How the themes are counted

One paper saying "this needs more study" tells you little. 52 separate papers raising the same open question is a finding about the field. The themes below are ordered by how many distinct papers raised them, most first, with "Other open questions" last. We count papers, not sentences, because one long paper can produce a dozen sentences on the same point.

Of the 369 studies in the library, 253 yielded at least one such sentence (455 from open-access full text, 49 from the abstract only). The rest either had no accessible text, or simply did not phrase an open question in a way we could quote without interpreting it — and we would rather miss one than invent one.

Where the papers disagree

These are not gaps everyone agrees on. In each pair below, two papers in this library point in different directions about what should happen next. Both quotes are verbatim.

Physical activity: is the open question whether it works, or which kind works best?

“Furthermore, our results on cognitive decline are in accordance with other longitudinal studies showing no association between physical activity and cognitive ageing.”

Physical activity, cognitive decline, and risk of dementia: 28 year follow-up of Whitehall II cohort study. · BMJ, 2017

“Future studies are needed to confirm current findings, explore the effects of different types of exercise training on outcomes in individuals with SVCI, identify moderators of exercise efficacy (e.g., biological sex), and examine the distinct mechanisms by which each exercise modality may exert its benefits.”

Resistance training and subcortical vascular cognitive impairment: A 12-month randomized trial. · Alzheimer's & Dementia, 2026

Both papers are asking for more exercise research, but not the same research. One reports no association with cognitive decline at all; the other treats the benefit as established enough that the next question is which modality and which mechanism.

Vision and hearing: replicate the association first, or start rolling out screening?

“While some US cohort studies have observed a significant association between vision impairment and dementia risk [ , ], other US and European longitudinal studies have failed to replicate these findings [ – ].”

A comprehensive evaluation on the associations between hearing and vision impairments and risk of all-cause and cause-specific dementia: results from cohort study, meta-analysis and Mendelian randomization study. · BMC Medicine, 2024

“Future studies should test whether vision screening or cataract surgery in those with co-occurring dementia risk factors are effective at reducing the risk of dementia.”

Visual Impairment, Eye Conditions, and Diagnoses of Neurodegeneration and Dementia. · JAMA Network Open, 2024

The same body of evidence is read two ways: one review notes that the vision-dementia association has failed to replicate across cohorts, while the proposed next steps elsewhere assume it holds and move to testing or implementing screening.

Repeat scans and tests to monitor disease: not supported, or the obvious next study?

“Cross‐sectional and longitudinal studies do not support the use of a subsequent amyloid PET to assess the degree of cognitive impairment or to monitor the rate of progression of the underlying AD pathological process.”

Updated appropriate use criteria for amyloid and tau PET: A report from the Alzheimer's Association and Society for Nuclear Medicine and Molecular Imaging Workgroup. · Alzheimer's & Dementia, 2025

“Additionally, future research should explore how the test can monitor disease as it progresses or how treatment responds with longitudinal studies [ ] .”

FDA approval of the Lumipulse G PTau217/β-amyloid 1-42 plasma ratio test: a new era in accessible Alzheimer's diagnosis. · Annals of Medicine and Surgery, 2025

The appropriate-use criteria for amyloid and tau PET state that the existing longitudinal evidence does not support repeat amyloid imaging for monitoring. An editorial on the newly approved blood test proposes studying exactly that use for blood biomarkers. Different tests - but the same unresolved question about whether repeat measurement tracks anything useful.

The mechanism is not understood 52 papers

The effect is measurable; the biology behind it is not settled. — 58 quoted sentences from 52 separate papers.

Show the other 52 quotes in this theme

Measurement, definitions, assays and standardisation 51 papers

Different teams measuring different things and calling them the same name. — 57 quoted sentences from 51 separate papers.

Show the other 51 quotes in this theme

Real-world delivery, cost and access 51 papers

Whether a result that held in a trial survives contact with an ordinary clinic. — 52 quoted sentences from 51 separate papers.

Show the other 46 quotes in this theme

Who was studied - diversity and generalisability 49 papers

Authors flag that their sample was narrow and that the result may not transfer. — 52 quoted sentences from 49 separate papers.

Show the other 46 quotes in this theme

Biomarker-defined, genetic and clinical subgroups 47 papers

Who benefits, not just whether anyone does. — 56 quoted sentences from 47 separate papers.

Show the other 50 quotes in this theme

Follow-up is too short to know if the effect lasts 42 papers

Papers repeatedly say their own follow-up window cannot answer whether a benefit persists. — 51 quoted sentences from 42 separate papers.

Show the other 45 quotes in this theme

Bigger samples and independent replication 27 papers

More people, and someone else repeating it. — 27 quoted sentences from 27 separate papers.

Show the other 22 quotes in this theme

Specific exposures, drugs and programmes named as worth testing 25 papers

Where authors do not just say 'more research' but name the thing they think should be tested. — 31 quoted sentences from 25 separate papers.

Show the other 25 quotes in this theme

Whether the association is causal is still open 18 papers

Observational signals that the authors themselves decline to call cause and effect. — 18 quoted sentences from 18 separate papers.

Show the other 12 quotes in this theme

Long-term safety and harms 14 papers

Adverse effects over a horizon longer than the trial. — 24 quoted sentences from 14 separate papers.

Show the other 18 quotes in this theme

The right dose, intensity, frequency and type is unresolved 13 papers

Especially for exercise, diet and other behavioural interventions: something works, but not how much of it. — 15 quoted sentences from 13 separate papers.

Show the other 9 quotes in this theme

When in life to intervene 13 papers

Midlife, preclinical, or after symptoms - the window is contested. — 13 quoted sentences from 13 separate papers.

Show the other 8 quotes in this theme

Better treatments and interventions still need developing 2 papers

Not whether a thing works, but that no good enough option exists yet. — 2 quoted sentences from 2 separate papers.

Show the other 1 quote in this theme

Combination and multidomain approaches 1 paper

Whether interventions add up, and which ones to combine. — 1 quoted sentence from 1 separate paper.

Other open questions 35 papers

Verbatim suggestions that did not fall into any theme above. They are published rather than discarded so the page does not quietly lose a question an author actually raised. — 47 quoted sentences from 35 separate papers.

Show the other 41 quotes in this theme

How these quotes were found

We searched the full text of every study in the library that has an open-access version, plus the abstracts of the rest, for the phrases researchers use when they are flagging an open question — "future studies", "further research", "remains to be determined", "remains unclear", "warrants further", "unknown whether", "open question", and similar. Each matching sentence was captured whole and then re-checked against the source text before being kept; anything that failed that check was dropped rather than repaired.

This means the page under-reports. A paper that phrases its open question without one of those signals contributes nothing here, and a paper behind a paywall contributes only what its abstract says. Missing a real suggestion is a much smaller problem than inventing one.

No health advice, and no causal claims. Nothing here says a treatment works, a behaviour prevents dementia, or that you should change anything. These are open research questions. For what the studies actually found, read the research summaries; see also the most-cited studies.

Full text: Europe PMC. Abstracts: PubMed. Retrieved 2026-09-24.