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Home › Research › Study types › Cohort or longitudinal study

Cohort and longitudinal studies in the research library

A cohort or longitudinal study follows a group of people over time and records what happens to them, which shows what comes before what but cannot by itself prove cause.

These counts and lists are worked out from the library itself each time the page loads. A score rates how much weight a study can bear — its design, journal, evidence and recency — not whether its result is good news. The study type is the one each record states; a record with no stated design is not counted here.

The 20 highest-scoring

  1. Donanemab in preclinical Alzheimer's disease: Screening and baseline data from TRAILBLAZER-ALZ 3 Alzheimer's & dementia : the journal of the Alzheimer's Association · 2025-09-01 · · Peer-reviewed
  2. Lifetime risk and projected burden of dementia Nature Medicine · 2025-01-13 · · Peer-reviewed

    This study estimates that about 42% of people who reach age 55 will develop dementia in their lifetime, with higher rates in women, Black adults, and APOE ε4 carriers. It projects that new dementia cases in the US will rise from about 514,000 a year in 2020 to about 1 million in 2060, which the authors say shows an urgent need for policies that support healthy aging and health equity.

  3. Diagnostic Accuracy of a Plasma Phosphorylated Tau 217 Immunoassay for Alzheimer Disease Pathology JAMA Neurology · 2024-03-01 · · Peer-reviewed

    A commercially available plasma p-tau217 immunoassay accurately identified biological Alzheimer's disease, comparable to cerebrospinal fluid biomarkers, with reproducible cut-offs across cohorts. Using a three-range reference reduced confirmatory testing by about 80%, which could make diagnosis less invasive and more accessible.

  4. Twenty-seven-year time trends in dementia incidence in Europe and the United States: The Alzheimer Cohorts Consortium Neurology · 2020-07-01 · · Peer-reviewed

    Pooling 7 population cohorts from Europe and the United States (49,202 people over 65, followed between 1988 and 2015), this study found the rate of new all-cause dementia cases fell by 13% per decade (95% CI 7–19%), consistently across the cohorts. The fall was larger in men (24%) than in women (8%, CI 0–15%). The authors say the causes of the decline are unknown and that the results still need to be checked in more geographically and ethnically diverse populations. This is a trend in how often new cases arise, not a test of any treatment.

  5. Assessment of Plasma Amyloid-β42/40 and Cognitive Decline Among Community-Dwelling Older Adults JAMA network open · 2020-12-01 · · Peer-reviewed
  6. The Impact of COVID-19 Confinement on Cognition and Mental Health and Technology Use Among Socially Vulnerable Older People: Retrospective Cohort Study Journal of medical Internet research · 2022-02-22 · · Peer-reviewed
  7. Astrocyte reactivity influences amyloid-β effects on tau pathology in preclinical Alzheimer's disease Nature Medicine · 2023-05-29 · · Peer-reviewed

    In three cohorts totalling 1,016 cognitively unimpaired individuals, amyloid-beta was associated with increased plasma phosphorylated tau and an Alzheimer's-like pattern of tau accumulation only in people positive for astrocyte reactivity. The findings suggest astrocyte reactivity as an upstream event linking amyloid-beta with initial tau pathology and may help select participants for trials, but no treatment is tested.

  8. Circulating Biomarkers of Neurodegeneration and All-Cause and Dementia-Specific Mortality Neurology · 2026-03-13 · · Peer-reviewed
  9. A comprehensive head-to-head comparison of key plasma phosphorylated tau 217 biomarker tests Brain · 2025-02-03 · · Peer-reviewed

    In a head-to-head comparison, the mass spectrometry-based %p-tau217WashU test performed significantly better than all immunoassays at identifying amyloid-PET, tau-PET, and cognitive abnormalities. The authors suggest %p-tau217 could serve as a stand-alone confirmatory test, while some immunoassays may be better suited as triage tests needing a second confirmation.

  10. Plasma p-tau217 and tau-PET predict future cognitive decline among cognitively unimpaired individuals: implications for clinical trials Nature Aging · 2025-03-28 · · Peer-reviewed

    Plasma p-tau217 and tau-PET performed similarly in predicting future cognitive decline among cognitively unimpaired individuals, and combining them was slightly better than either alone. Using plasma p-tau217 first and then tau-PET reduced the number of participants needed for a clinical trial by 94%, which could make preclinical Alzheimer's trials more efficient.

  11. Changes in Alzheimer Disease Blood Biomarkers and Associations With Incident All-Cause Dementia JAMA · 2024-10-15 · · Peer-reviewed

    In community-dwelling adults, midlife hypertension and diabetes were associated with faster increases in NfL and GFAP, while only Alzheimer's-specific biomarkers in midlife showed long-term associations with late-life dementia. All plasma biomarkers measured in late life were associated with late-life dementia, with NfL showing the largest association.

  12. Prediction of Longitudinal Cognitive Decline in Preclinical Alzheimer Disease Using Plasma Biomarkers JAMA neurology · 2023-04-01 · · Peer-reviewed

    This study followed people from two research cohorts, BioFINDER-1 and WRAP, who had amyloid in the brain but were described as cognitively unimpaired: 171 people in the main analyses. It asked whether blood markers predict later memory and thinking decline at this "preclinical" stage. The authors conclude that the blood test plasma P-tau217 "may be used as a complement to CSF or PET" when choosing participants for trials of new disease-modifying treatments. That is a finding about trial recruitment, not about a treatment, and our record does not include the figures showing how well the test predicted decline.

  13. Greater White Matter Hyperintensity Volume Is Associated with the Number of Microhemorrhages in Preclinical Alzheimer's Disease The journal of prevention of Alzheimer's disease · 2024-01-01 · · Peer-reviewed
  14. Prognostic value of plasma %p-tau217 in cognitively unimpaired older adults Alzheimer's & dementia : the journal of the Alzheimer's Association · 2026-07-01 · · Peer-reviewed
  15. Associations between trajectories of plasma biomarkers for Alzheimer's disease, brain structures, and cognitive function: a prospective cohort study in the UK Biobank Molecular psychiatry · 2025-08-28 · · Peer-reviewed
  16. Racial and Ethnic Differences in the Population-Attributable Fractions of Alzheimer Disease and Related Dementias Neurology · 2024-01-17 · · Peer-reviewed
  17. Herpes Zoster Vaccination and Dementia Occurrence (Australian natural experiment) JAMA · 2025-06-17 · · Peer-reviewed

    This Australian natural experiment examined whether herpes zoster vaccination affects the chance of a new dementia diagnosis, using eligibility based on date of birth. The text provided does not report the study's results, so it is not possible to say whether vaccination affected dementia occurrence.

  18. Deferiprone in Alzheimer Disease: A Randomized Clinical Trial JAMA neurology · 2025-01-01 · · Peer-reviewed

    In this trial of 81 participants with Alzheimer disease, deferiprone accelerated cognitive decline on the primary outcome compared with placebo, driven by worsening performance on executive function tests, even though it decreased iron in the hippocampus. Hippocampal volume loss was not affected, and exploratory analysis found increased volume loss in some other brain regions with deferiprone.

  19. Association of Lifestyle and Genetic Risk With Incidence of Dementia JAMA · 2019-08-01 · · Peer-reviewed

    In a cohort of 196,383 older adults without dementia, followed for a median of 8 years, both high genetic risk and an unfavourable lifestyle were associated with more dementia. Among people at high genetic risk, 1.13% of those with a favourable lifestyle developed dementia, against 1.78% with an unfavourable one (hazard ratio 0.68). The study is observational and did not test changing anyone's lifestyle. It shows an association, not proof that a healthy lifestyle prevents dementia.

  20. Blood phosphorylated tau 181 as a biomarker for Alzheimer's disease: a diagnostic performance and prediction modelling study using data from four prospective cohorts The Lancet. Neurology · 2020-05-01 · · Peer-reviewed

    This study, using data from four prospective cohorts, tested how well a blood measure of phosphorylated tau 181 (p-tau181) matched established spinal-fluid (CSF) and PET brain-scan markers of Alzheimer's disease, and whether it could be used in prediction models of change over time. Our record holds only the study's methods, not its results, so it cannot tell you how accurate the blood test was — check the original paper before drawing any conclusion. It evaluates a diagnostic test and does not test any treatment, cure or prevention.

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