How common it is: research in the library

• 522studies on this subject, of 27,380 in the library
• 490peer-reviewed
• 1981–2026years published
• 57median usefulness score out of 100

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. How we score a study. For a plain-English guide to this subject, see Alzheimer's in numbers.

1. Lifetime risk and projected burden of dementia Nature Medicine · 2025-01-13 · usefulness score 85/100 · Peer-reviewed
   • Genetics

   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.

2. Delirium in elderly patients and the risk of postdischarge mortality, institutionalization, and dementia: a meta-analysis JAMA · 2010-07-01 · usefulness score 82/100 · Peer-reviewed

   Pooling studies of older patients, this 2010 meta-analysis found that people who had delirium were more likely to have died about two years later (hazard ratio 1.95), to have moved into an institution (odds ratio 2.41), and to have developed dementia over about four years, and that these links held "independent of important confounders, such as age, sex, comorbid illness or illness severity, and baseline dementia." The dementia estimate comes from only 2 studies and is very imprecise (odds ratio 12.52, 95% CI 1.86–84.21), so it shows a direction of risk rather than a reliable size. This is an association: the study did not test whether preventing or treating delirium changes any of these outcomes.

3. Twenty-seven-year time trends in dementia incidence in Europe and the United States: The Alzheimer Cohorts Consortium Neurology · 2020-07-01 · usefulness score 82/100 · Peer-reviewed
   • Risk Factors

   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.

4. Conjugated equine estrogens and incidence of probable dementia and mild cognitive impairment in postmenopausal women: Women's Health Initiative Memory Study JAMA · 2004-06-01 · usefulness score 80/100 · Peer-reviewed
   • Early Stage
   • Risk Factors

   In the estrogen-alone arm of the Women's Health Initiative Memory Study, 28 women assigned to conjugated equine estrogens and 19 assigned to placebo were diagnosed with probable dementia (hazard ratio 1.49; 95% CI 0.83–2.66). That range includes no difference, so this trial on its own did not show a statistically significant effect. When the data were pooled "per the original WHIMS protocol", the overall hazard ratio was 1.76 (95% CI 1.19–2.60; P = .005). Neither result suggests this hormone protected against dementia.

5. Risk of dementia and mild cognitive impairment in older people with subjective memory complaints: meta-analysis Acta psychiatrica Scandinavica · 2014-09-13 · usefulness score 80/100 · Peer-reviewed
   • Early Stage
   • Risk Factors

   This meta-analysis found that older people with subjective memory complaints but no objective deficits were about twice as likely to develop dementia as those without such complaints, with annual conversion rates of 2.33% to dementia and 6.67% to mild cognitive impairment. It identifies a group at higher risk but does not test any treatment, cure, or prevention.

6. Conjugated equine estrogens and global cognitive function in postmenopausal women: Women's Health Initiative Memory Study JAMA · 2004-06-01 · usefulness score 80/100 · Peer-reviewed
   • Clinical Trials

   In a randomized, placebo-controlled trial of 2,808 women aged 65–79 who had had a hysterectomy, those given daily conjugated equine estrogen scored 0.26 points lower on average on a global thinking test (3MSE) than those on placebo over about 5.4 years. The study concluded that, for women 65 or older, "hormone therapy had an adverse effect on cognition, which was greater among women with lower cognitive function at initiation of treatment." It measured test scores, not Alzheimer's diagnoses, and does not show how estrogen affects younger women.

7. Global prevalence of dementia: a Delphi consensus study Lancet (London, England) · 2005-12-01 · usefulness score 79/100 · Peer-reviewed

   This consensus study estimates how many people have dementia worldwide and projects that the number will grow substantially by 2040, especially in developing countries. It provides no information about treating, curing or preventing Alzheimer's disease.

8. Effectiveness of a 6-year multidomain vascular care intervention to prevent dementia (preDIVA): a cluster-randomised controlled trial Lancet (London, England) · 2016-07-26 · usefulness score 79/100 · Peer-reviewed
   • Clinical Trials
   • Risk Factors

   This randomised controlled trial found that a nurse-led, multidomain vascular care intervention did not reduce the incidence of all-cause dementia in an unselected population of older people. The intervention did not work for preventing dementia in this trial.

9. Effect of Aspirin on All-Cause Mortality in the Healthy Elderly The New England journal of medicine · 2018-09-16 · usefulness score 79/100 · Peer-reviewed
10. Prevalence of neuropsychiatric symptoms in dementia and mild cognitive impairment: results from the cardiovascular health study JAMA · 2002-09-01 · usefulness score 78/100 · Peer-reviewed
    • Early Stage

    This study found that many people with mild cognitive impairment and dementia had neuropsychiatric symptoms such as depression, apathy and irritability in the previous month. It is a descriptive count of symptoms and does not test any treatment, cure or prevention for Alzheimer's disease.

11. Frontotemporal dementia and its subtypes: a genome-wide association study The Lancet. Neurology · 2014-07-01 · usefulness score 78/100 · Peer-reviewed
    • Genetics
    • Other Dementias

    This genetic study found new gene regions linked to frontotemporal dementia, pointing to immune system processes and possibly lysosomal and autophagy pathways. The authors state these findings need to be replicated, so no treatment or prevention follows yet.

12. Cumulative use of strong anticholinergics and incident dementia: a prospective cohort study JAMA internal medicine · 2015-03-01 · usefulness score 77/100 · Peer-reviewed
    • Risk Factors
    • Side Effects

    In 3,434 adults aged 65+ in Seattle followed for a mean of 7.3 years, those who had filled more anticholinergic prescriptions over the previous 10 years were more likely to develop dementia and Alzheimer's, with risk rising as cumulative dose rose. The drugs most used were tricyclic antidepressants, first-generation antihistamines and bladder antimuscarinics. This is an association, not proof the drugs cause dementia or that stopping them prevents it. The authors call for more awareness among clinicians and older adults so these drugs are used less over time.

13. Leisure-time physical activity at midlife and the risk of dementia and Alzheimer's disease The Lancet. Neurology · 2005-11-01 · usefulness score 77/100 · Peer-reviewed
    • Risk Factors
    • Lifestyle
    • Genetics

    Among 1,449 people aged 65–79 who were re-examined in 1998, an average of 21 years after a midlife survey, those who had done leisure-time physical activity at least twice a week in midlife had lower odds of dementia (odds ratio 0.48, 95% CI 0.25–0.91) and Alzheimer's disease (0.38, 0.17–0.85), after adjusting for factors including age, education, APOE genotype, vascular disorders, smoking and alcohol; the association was "more pronounced" in APOE ε4 carriers. This is an observational cohort, not a trial, so it shows an association rather than proof that exercise lowers risk; the authors conclude that regular activity "may reduce the risk or delay the onset" of dementia.

14. A systematic review of prevalence studies of dementia in Parkinson's disease Movement disorders : official journal of the Movement Disorder Society · 2005-10-01 · usefulness score 77/100 · Peer-reviewed
    • Other Dementias

    This review pooled 12 studies of people with Parkinson's disease (1,767 patients) and 24 studies of dementia types (4,711 patients). It found that 24.5% of people with Parkinson's had dementia, and 31.1% in the four studies that best met its quality criteria. Parkinson's disease dementia made up 3.6% of all dementia and affected an estimated 0.2 to 0.5% of people aged 65 and over. The authors note "significant methodological variations between studies". These are point-in-time prevalence figures, not anyone's personal risk, and the review tests no treatment.

15. Global Prevalence of Young-Onset Dementia: A Systematic Review and Meta-analysis JAMA neurology · 2021-09-01 · usefulness score 77/100 · Peer-reviewed

    Drawing on 95 studies, this review estimates that 119 per 100,000 people aged 30 to 64 worldwide live with young-onset dementia, about 3.9 million people. Prevalence was similar in men and women and lower in high-income than in middle-income countries. The authors say the figures should help policymakers plan enough care for this group, while noting that data from low-income countries and younger age ranges remain scarce.

16. Midlife cardiovascular risk factors and risk of dementia in late life Neurology · 2005-01-01 · usefulness score 76/100 · Peer-reviewed
    • Risk Factors

    In 8,845 members of a health plan who had check-ups at age 40–44 (1964–1973), those with high cholesterol, hypertension, diabetes or who smoked were each more likely to have a dementia diagnosis in their medical records in 1994–2003 (hazard ratios 1.24 to 1.46). Risk rose with the number of factors: compared with none, the hazard was 1.27 with one factor and 2.37 with all four (95% CI 1.10 to 5.10, a wide range). This is an observational study of dementia in general, not Alzheimer's specifically, and it does not test whether treating these factors lowers dementia risk.

17. Global Prevalence of Young-Onset Dementia: A Systematic Review and Meta-analysis JAMA Neurology · 2021-09-01 · usefulness score 74/100 · Peer-reviewed

    Roughly 3.9 million people worldwide under age 65 are living with young-onset dementia, about double earlier estimates, with rates climbing steeply from the early 30s to the early 60s. This highlights a group of patients often missed or misdiagnosed because dementia is usually thought of as a disease of old age.

18. 6-month consequences of COVID-19 in patients discharged from hospital: a cohort study Lancet (London, England) · 2021-01-08 · usefulness score 74/100 · Peer-reviewed

    This study followed patients discharged after COVID-19 and found some had ongoing problems with lung diffusion, anxiety or depression, fatigue, and kidney function. It does not address Alzheimer's disease treatment, cure or prevention.

19. Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit JAMA · 2004-04-01 · usefulness score 74/100 · Peer-reviewed

    In 275 ventilated ICU patients at one US hospital, 81.7% of those who could be assessed developed delirium, and they had higher 6-month mortality than those who did not (34% vs 15%) and stayed in hospital 10 days longer. The authors found delirium was an independent predictor of death and longer stay after adjusting for coma, sedatives and painkillers. This is an association in critically ill patients, not a test of any treatment, and it does not study Alzheimer's disease.

20. Nonsteroidal antiinflammatory drugs and the risk of Alzheimer's disease The New England journal of medicine · 2001-11-01 · usefulness score 74/100 · Peer-reviewed
    • Risk Factors
    • Treatments

    In 6,989 people aged 55 or older who were followed for an average of 6.8 years, those whose pharmacy records showed 24 months or more of NSAID use had a lower risk of Alzheimer's disease (relative risk 0.20, 95% CI 0.05 to 0.83). Shorter use showed no clear difference, and no NSAID use was linked to lower vascular-dementia risk. Because this is an observational study and the estimate is very imprecise, the authors say only that long-term use "may protect" against Alzheimer's disease; it does not show that taking NSAIDs prevents it.

See all 522 studies in How common it is, with filters →

• Selective vulnerability of human basal forebrain subsystems in ageing and neuropsychiatric disorders medRxiv · 2026-10-15 · usefulness score 16/100 · Preprint — not yet peer-reviewed
• Enhancing Neurodegeneration Awareness and Care for the Elderly in Saudi Arabia, UAE, Oman, and Qatar: Challenges, Policy Gaps, and Future Directions Preprints.org · 2026-10-13 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Policy
  • Digital Tools
• Cognitive and Renal Outcomes of Finerenone in Older Adults With Heart Failure With Preserved Ejection Fraction: A Real-World Cohort Study Research Square · 2026-10-06 · usefulness score 16/100 · Preprint — not yet peer-reviewed
• Study of Ancestry, Health, Environment, and Late-Life Neurodegeneration (SAHEL) medRxiv (preprint) · 2026-09-24 · usefulness score 16/100 · Preprint — not yet peer-reviewed
• Parkinson’s Disease Onset in Light of Acquired Irreversible Piezo2 Channelopathy Preprints.org · 2026-09-23 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Other Dementias
• Population-scale burden analysis of rare damaging coding variants identifies novel risk genes for Alzheimer's disease and related dementias and Parkinson's disease and related disorders medRxiv (preprint) · 2026-09-18 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Genetics
  • Other Dementias
• Changing Landscape of Alzheimer’s Disease Mortality in the United States (1979– 2023): A CDC WONDER Analysis of Epidemiological Shifts, Disparities and ARIMA-Based Projections to 2050 Research Square · 2026-09-17 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Health Equity
• Antihypertensive Medication Class and Incident Alzheimers Disease and Related Dementias: External Replication Across Two Independent Healthcare Data Sources-the Vanderbilt EHR Synthetic Derivative and US Medicare Claims medRxiv (preprint) · 2026-09-17 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Treatments
  • Policy
• Excess hypoglycaemia-related hospitalisation in older adults with comorbid type 2 diabetes and dementia: a UK Biobank cohort study medRxiv (preprint) · 2026-09-16 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Care Services
• Subjective word-finding complaints in older adults: Development and preliminary psychometric evaluation of a novel self-reported questionnaire medRxiv (preprint) · 2026-09-14 · usefulness score 16/100 · Preprint — not yet peer-reviewed
  • Early Stage

All 522 studies in How common it is, newest first →

Studies by year published

Counts the 522 studies with a usable publication date. The library is a large sample of published work, not a complete index, so these counts describe the library, not the whole field.

• Getting a diagnosis
• Biomarkers
• Clinical trials
• Prevention and risk
• Caregiving
• Costs and economics
• Genetics
• Laboratory science
• Disease mechanisms
• Vascular contributions
• Prevention trials
• Clinical safety
• Health systems and care delivery
• End-of-life care
• Risk factors
• Digital health tools
• Treatments
• Disparities
• Mild cognitive impairment
• Risk genes beyond APOE
• Brain scans and imaging
• TREM2 and immune genetics
• Cognitive tests and assessment
• Lewy body dementia
• Down syndrome and Alzheimer's
• Long-term cohort studies
• Inflammation and the immune system
• Tau biomarkers
• Brain tissue and pathology
• Drug development
• Hippocampus size on brain scans

All subjects, side by side →