Being screened out of a dementia study is common, and it usually says more about the trial's design than about you. Most eligibility rules exist to keep the science interpretable and the participants safe — but applied to real older adults, they rule out the large majority of people who volunteer. Eligibility criteria come in two halves: inclusion criteria, the things you must have (a diagnosis, an age, a test score), and exclusion criteria, the things that disqualify you (other conditions, certain medications, scan findings). Learning to read both before you apply turns a demoralizing rejection into a filtering step you can do yourself in ten minutes.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What the criteria usually say
- Why so many people are screened out
- The criteria do not exclude at random
- How to read a study listing before you apply
- What is changing, and what it means for you
- Frequently Asked Questions
What the criteria usually say
The same short list of requirements repeats across almost every trial. Across 608 phase II and III Alzheimer's drug trials registered on ClinicalTrials.gov, a 2026 analysis in the *Journal of Prevention of Alzheimer's Disease* found the five most common criteria were no other central nervous system disorder affecting cognition (84%), participation of a caregiver (72%), a score within a set range on the Mini-Mental State Examination (66%, most often 24–30 out of 30), no contraindication to study procedures (61%), and age (53%, most often 55–85). The pattern holds in publicly funded research too.
A 2024 review of 196 Alzheimer's and related dementias trials funded by the National Institute on Aging, published in *Scientific Reports*, found age cutoffs in 87% of them, specified neurologic disorders in 65% and psychiatric disorders in 61%. Read that list again and notice what it is really asking for: a person with dementia and essentially nothing else going on, plus a second person willing to attend visits with them. That is not a description of a typical 78-year-old.
Why so many people are screened out
The exclusions are individually reasonable and collectively enormous. When researchers applied the A4 prevention trial's medical exclusion criteria to 3,695 older adults in the nationally representative Health and Retirement Study using linked Medicare claims, the analysis by Ashford and colleagues in *Alzheimer's & Dementia: TRCI* ruled out 74% of them on medical history alone — most often for cardiovascular conditions. The picture is similar in Europe.
In the population-based Rotterdam Study of 968 people with mild cognitive impairment or early Alzheimer's dementia (mean age 75, 56% women), Claus and colleagues reported in *Alzheimer's & Dementia* that full eligibility for amyloid-lowering therapy trials ranged from 8% for aducanumab and lecanemab to 15% for donanemab. About 40% failed on amyloid negativity — no amyloid protein found on testing — and roughly a third were excluded by brain MRI findings alone, mostly cerebral small-vessel disease. The specific clinical exclusions doing the work in Rotterdam were ordinary chart entries, not rare diseases: If you take a blood thinner and have a history of heart trouble, you have already hit two of the five.
- cardiovascular disease — 35.2%
- anticoagulant use — 31.2%
- psychotropic or immunological medication — 20.4%
- psychiatric disease — 15.9%
- lack of social support — 15.6%
The criteria do not exclude at random
This is the part that matters most for readers who feel personally singled out. In the Health and Retirement Study analysis, older age, female sex, fewer years of education, lower net worth and a BMI of 30 or above each independently raised the odds of being ineligible. The filter tilts the trial population toward people who are wealthier, healthier and better educated than the population that actually develops dementia. Screening data show the same skew by race and ethnicity.
In the ENVISION aducanumab confirmatory trial, US screen-failure rates reached 90% among African American candidates (N=75) and Hispanic candidates (N=110), against 75% among non-Hispanic White candidates. The leading reason in both groups was not meeting NIA-AA criteria for MCI or mild Alzheimer's — 55% and 58% — followed by unconfirmed amyloid pathology, exclusionary MRI findings and, for a small share, no identified care partner. Sex differences trace to how people arrive at clinic rather than to biology alone. In the Amsterdam Dementia Cohort of 3,835 patients seen between 2000 and 2024, women were less eligible than men on the five standard criteria, driven mainly by absence of a caregiver and a lower MMSE score at presentation. A woman who outlived her spouse and reached the memory clinic later fails two rules that were written as neutral thresholds.
How to read a study listing before you apply
Every registered study posts its inclusion and exclusion criteria publicly. Work through them in the order most likely to stop you, so you spend your time on studies you can actually enter.
The National Institute on Aging advises checking those posted criteria first, then contacting the study coordinator with questions about the study's purpose, procedures, time commitment and risks — and telling your own clinician before you enroll. Its clinical trials finder at Alzheimers.gov lists studies with their criteria attached, including genetic profile requirements where they apply.
- **Age and stage.** Check the age band and the required diagnosis. "Mild cognitive impairment or mild Alzheimer's dementia" excludes both people with no diagnosis and people past the moderate stage.
- **Cognitive score range.** An MMSE floor screens out people whose disease has advanced; a ceiling screens out people who are doing too well. Ask your clinician what your most recent score was.
- **Other conditions.** Look for the cardiovascular, psychiatric and neurologic exclusions. These disqualify more candidates than anything else on the medical side.
- **Medications.** Anticoagulants, psychotropics and immunological drugs appear repeatedly. A drug you take for an unrelated reason can end the conversation.
- **Imaging and biomarkers.** Many trials require confirmed amyloid and a clean-enough MRI. Small-vessel disease on a scan is a frequent, and usually unexpected, stopping point.
What is changing, and what it means for you
Regulators have started treating narrow enrollment as a problem for the sponsor to solve rather than a fact of research life. In June 2024 the FDA published draft guidance requiring sponsors to submit Diversity Action Plans that specify enrollment goals and the concrete measures they will take to reach them, for studies supporting approval; it applies to studies whose enrollment begins 180 days after the final guidance publishes. That changes recruitment effort and site selection.
It does not loosen the medical exclusions that screen out three-quarters of older adults, and no policy will make an anticoagulant compatible with a drug that carries bleeding risk. The practical implication is to treat eligibility as study-specific rather than as a verdict. The Rotterdam numbers ranged from 8% to 15% across three drugs in the same population, which means a criterion that stopped you at one trial may not exist at the next. Observational studies, registries, caregiver-focused research and non-drug trials generally carry far lighter exclusion lists than amyloid-lowering drug trials, and they still need participants who look like the people who get dementia.
Frequently Asked Questions
Does failing screening for one trial mean I will fail others?
No. Eligibility for amyloid-lowering therapies in the Rotterdam Study ranged from 8% to 15% depending on which drug's criteria were applied to the same group of people. Criteria differ by drug, by sponsor and by study type.
Why do so many trials require a caregiver or study partner?
A study partner reports on daily function and memory changes the participant may not notice, and helps with visit attendance and dosing. It appeared in 72% of the 608 phase II and III trials reviewed, which makes it one of the most common single requirements in the field.
What is an MMSE range, and why does a high score disqualify someone?
The Mini-Mental State Examination is a 30-point cognitive screening test. A common trial window is 24–30, which targets mild impairment; scoring below the floor usually means the disease is too advanced for the study's design, while trials studying later stages set their windows lower.
