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For a disease which (to my knowledge) can’t be slowed down or reversed, I think it’s a fair question why we would want to detect Alzheimer’s. Maybe there are other reasons, but my suspicion is that we will be able to, and an easy detection method significantly widens the pool of subjects to study later on.

If it turns out that driving a Prius on Tuesdays slows down Alzheimer’s, a larger pool of subjects would allow us to figure that out.

I would personally want to know as early as possible, so I could get my affairs in order and register my wishes around end of life care and euthanasia while I am still recognised as having full mental capacity.

It's also better for people around the Alzheimer's patient, as it will let them understand why someone's personality and behaviours may be changing, and possibly let them be bit more forgiving of such changes. It will also give family more time to plan and understand the health and community services and support are offered wherever they live.

I know two people who have been taking the new monoclonal antibody treatment for it. One who was a bit further along when she started, and did not show any significant improvement. The one who started while she was still in the early stages has completely arrested her descent. She hasn't recovered much of what she already lost, but she's still able to live independently and enjoy life, and her mental acuity scores are (slightly) better than they were last year. That's a hell of a thing.
It's very useful to understand what you're struggling from even if it's not curable. It explains your symptoms, your experience and help you understand what you're going through. Understanding that you're suffering from something incurable is also helpful in not looking for other ineffective methods to cure a mysterious illness.
Most people get a dementia (or related) diagnosis after they are deep enough in it so that they cant do much about it or get their affairs in order.

My grandfather had a "fall" at work, he then left that job, and held down 2 more engineering jobs before he was diagnosed with a stroking condition and subsequent dementia. I got the distinct impression he thought he had more time, but rapidly declined.

If he knew he was short of time before his rapid decline he probably would have done things differently. Like not buying a house he would later have to sell to pay for aged care.

If he knew he was at risk of a workplace accident he probably wouldn't have worked as an after hours safety engineer at a major treatment plant, where if the worst had happened he could have endangered others.

> why we would want to detect Alzheimer’s

At a personal level, I've been through this with my grandfather.

I want to know. My family wants to know. I want to prepare because there are things I want to do today that I know I won't be able to do in the future.

In many ways, it's just like many terminal cancer diagnoses. You're going to lose that person, but you have some time.

The accuracy of this test is nowhere nearly good enough to do population-wide screening. The clinical setting for this test is memory clinics in which Alzheimers is already relatively highly likely differentially, and even there you're going to get a surprising number of false positives.

(There's enough info in the supplemental link on this page to have an LLM do the Bayes math for you.)

> doctors correctly diagnosed Alzheimer's in 75.5% of cases, but when incorporating blood test results, diagnostic accuracy increased to 94.5%

These patients are already seeing doctors. Would you rather your doctor to hide the diagnosis just because your disease isn't curable (for now)? It's not like we're testing the whole population in masse.

There are more personal practical reasons too.

Even though it cannot be reversed or eradicated (yet, let's hope) detection can allow individuals to adopt interventions that help either adjust their lives to better cope with its progression or help mitigate some of the detrimental behavioral consequences. In addition, if you have family to care for it may be impetus to get certain things in order for them before later stages of the disease, etc. It's horrible and bleak, but I could certainly see why one might want to know.

In the lucky case, it can also relieve anxiety. Even though false negatives may still be possible, receiving a negative detection might give people who have anxiety about certain symptoms relief, since they can rule out (rightly or wrongly) a pretty severe disease.

Being able to know someone's risk factor would be important for how we treat elderly people. I know someone who is 85 and super sharp (previously worked as a corporate accountant and banker), they still have a better memory than a lot of 40-50 year olds, and yet they are constantly harassed by eldercare "agents" for the state because whenever they make a investment decision that is even slightly questionable they get reported to the state by the bank. Sometimes the bank refuses to authorize transactions. If they could conclusively prove they aren't at risk I think they would be left alone much more often.
If a loved one is suffering from this, this diagnostic would allow for interventions such as guardianship to assume financial and logistical responsibility for them with less subjective decisioning based on observations alone.
If the patient still has periods of lucidity but the disease is suspected to be advancing, knowing they have it could prompt them to get their legal affairs in order.
> For a disease which (to my knowledge) can’t be slowed down or reversed, I think it’s a fair question why we would want to detect Alzheimer’s.

Getting an accurate diagnosis is always important. Cognitive decline could be caused by other problems, some of which are more treatable than others.

If this test came back negative it would suggest extra testing to rule out other conditions like a brain tumor or hydrocephalus.

> For a disease which (to my knowledge) can’t be slowed down or reversed, I think it’s a fair question why we would want to detect Alzheimer’s. Maybe there are other reasons, but my suspicion is that we will be able to, and an easy detection method significantly widens the pool of subjects to study later on.

Your point at the end is essentially correct. There's a couple of reasons that come to my mind:

Early detection lets us test cures more quickly. You can see if the treatment is working without waiting 30 years for symptoms to develop or not. If prevention is all that works, we can verify lifestyle changes, again without having to wait 30 years for symptoms to develop.

Early detection means there's more of a chance of any future treatment succeeding and the patient returning to a normal life. Think of early detection of cancer or heart disease meaning you can be treated with less risky medication and procedures and minimise the damage being done.

I assume this is hugely beneficial for research on intervention methods, not for treatment. I think everyone is focusing on "I'd rather know" but imagine if you could get larger populations with a diagnosis earlier on, how impactful that would be for testing an intervention?
there are treatments that can help slow progression, especially if it's found early.
To rule out Alzheimers when you wonder whether your recent episodes of forgetfulness have an underlying medical cause.

That aside, some moderately effective drugs have recently been approved that can slow down the disease in its early stages. And even if you are no candidate for these: you can start organising the life around you while you still can. Like moving to an assisted living facility.

Having struggled with hard to diagnose health issues before, I can’t emphasize enough how much of a relief it is to put a name on the disease that is causing you so much harm.

It is frankly shocking to think disease diagnosis would be a useless thing

Not saying anything about the article at-hand, but assuming we were able to detect it with such certainty, I think it would greatly increase the funding, rigor, and breadth or research devoted to finding a cure or treatment that actually worked.
For 20-ish% of Alzheimer's patients, the Shingles vaccine may be a treatment. This has been suspected for a few years now but has received recent confirmation studies.

https://www.alzheimers.org.uk/news/2025-11-18/promising-rese...

This again?

The test is optional. Feel free to skip it.

Tell 50 million people they’re likely to have Alzheimer’s then tell them where to donate towards a cure, or treatments to slow it by a decade.

Well, the AI CEOs are telling we will have AGI in ~5 years, so with millions of agents with AGI this thing should be sorted soon ;)
> For a disease which (to my knowledge) can’t be slowed down or reversed

There's Lecanemab and Donanemab. The effects are modest however.

This disease is in my family, honestly not sure I would want to know if I will get it.
Even without a cure, there's still a lot of practical value in knowing earlier
I understand the "detect deadly progression but no cure" problem; this was the same rationale people used when Huntington disease could be verified in diagnostics. Many people don't want to know, but some want to know, in particular as you can manage some things here or there - diet affects many things, for instance, even aside from metaboic genetic defects. And for any (molecular) therapy at a later time you need to understand the molecular basis to some extent. Some things can be found out via trial and error (vaccination and before) but for some disease that can not work. Alzheimer is quite complex.
We have no cure now but that may change and depend on early detection just as taking meds now can slow the onset. I don’t want to know makes no sense to me. You would plan your whole life differently and it would actually be quite liberating once you’d come to terms with it.
“We have no cure. I don’t want to know.”

If astronomers announced that a large asteroid might strike Earth in twenty years, and that we currently had no way to deflect it, nobody would respond by saying, “Come back when you already have the rocket.” We would immediately build better telescopes to track it precisely, refine its trajectory models, and begin developing propulsion systems capable of interception. You do not wait for the cure before improving the measurement. You improve the measurement so that a cure becomes possible, targeted, and effective.

Medicine is no different. Refusing to improve early, probabilistic diagnosis because today’s treatments are modest confuses sequence with outcome. Breakthroughs do not emerge from vague labels and mixed populations. They emerge from precise, quantitative stratification that allows real effects to be seen. The danger is not that we measure too early. It is that we continue making irreversible clinical and research decisions using imprecise, binary classifications while biological insight and therapeutic tools are advancing rapidly. Building the probabilistic layer now is not premature. It is how we make future intervention feasible.

This analogy has a rather fatal flaw, which is that we already know people who've gotten Alzheimer's, and we also know for a fact people will continue to fall victim to it, at a pretty predictable rate. i.e. the detection has already happened! Anyone who was waiting for a potential victim to appear before researching the cure already has all the reasons they need to research it. Detecting whom exactly the next victim is going to be isn't really going to change anything as far as researching a treatment or cure goes. (Unless the person is super important or popular or rich, I guess?)

This is absolutely nothing like the asteroid example, where knowing that anybody is going to fall victim to it would itself be news of astronomical proportions. Previously there was a high chance the event wouldn't happen, and now it seems likely it will, so that entirely change the calculus of your priorities.

This just completely destroys the analogy. (There are other reasons it doesn't fit too, but one is enough.)

> “We have no cure. I don’t want to know.”

> If astronomers announced that a large asteroid might strike Earth in twenty years, and that we currently had no way to deflect it, nobody would respond by saying, “Come back when you already have the rocket.”

I don’t think the analogy fits, for a couple reasons.

1. People not wanting to know whether they have Alzheimer’s is because of the fear of a fate worse than death — living with Alzheimer’s.

2. People not wanting to know whether they have Alzheimer’s is not the same was not wanting a way to detect it. As you said, being able to measure it may help lead to a cure/treatment. I doubt people are against improving detection — they may just not want the detection to be applied personally.

I want to know so that I can make plans. Including end of life plans, in all senses.
PSA to those with family affected by dementia/Alzheimer's at a relatively early age (say <70yo): Get them tested for STDs, specifically Syphilis.

Left untreated for a very long time (decade+), it spreads to the brain and causes dementia among other things. Older generations with stigmas, taboos, or from lower educational backgrounds seem (to me) less likely to get tested, so it seems plausible.

Source: Have recently discovered this myself with a family member from their neurologist.

A detail, but an important one: the blood test brought the initial diagnosis closer to the final one. The result reflects the agreement between both diagnoses. The usefulness of the blood test depends on the quality of the final diagnosis, which can still be wrong.
Paper is at Springer Nature Link: https://link.springer.com/article/10.1007/s00415-026-13676-6
Alarm bells go up. 94.5% in itself is suspicious. It insinuates precision. I highly doubt you can go anywhere near 0.5% correctness.
Maybe I've misunderstood something, but how can they know the accuracy of the test? It is the best test out there, so if it misses a diagnosis, how do they reliably catch the false negative?
Could earlier diagnoses contribute to finding causes and treatments?
I'd be curious to see how it performs outside of a specialist neurology setting and in larger, more diverse populations
https://pmc.ncbi.nlm.nih.gov/articles/PMC8755961/

"A narrative review on the effects of a ketogenic diet on patients with Alzheimer's disease"

https://www.sciencedirect.com/science/article/pii/S127977072...

"Effects of ketogenic diet on cognitive function of patients with Alzheimer's disease: a systematic review and meta-analysis"

And anecdotes from the field:

https://www.youtube.com/watch?v=s86CFw0qhVc

Revolutionizing Assisted Living: Hal Cranmer's Ketogenic & Carnivore Approach to Senior Wellness / Metabolic Mind

so 94,5% sensitivity, or specificity? this thing with medical testing and false positives is tricky
Since the recent discoveries about Shingles Vaccine delaying dementia https://hsph.harvard.edu/news/link-between-shingles-vaccine-...

One of interesting checks in this study might be to check when (if) any of the participants had taken this vax and what the impact might be on an Alzimer's diagnosis.

This needs to include life-changing false positive rates. Imagine being given a diagnosis like this - people around you who know and any corporations who can sniff it out by snooping on your communications can lead to much rejection early in life. What happens when the diagnosis is as positive when it shouldn’t have been?
Sorry, but the test hasn't been shown to be 94.5% accurate. The study was structured as: 1. neurologist makes clinical diagnosis using usual tools and records most likely diagnosis and their confidence in it 2. new p-tau test is done. 3. neurologists reassess their confidence, and change their mind in many cases. There is no "gold standard" here (tough to have in AD) and not even a period of clinical follow-up to assess for any interval change. The study shows that patients got reclassified, but never showed that such reclassification was more accurate than the initial one, and by how much. There is an implication that because in a different, retrospective study the test did show some accuracy, that it would be helpful in this new situation. But that's about it, and different than directly showing this to be the case.
This is Theranos levels of marketing.
Great but the big problem is how to actively treat it. Sleep is a huge factor and that’s a problem for us insomniacs :(
40 hz ultrasounds are part of the remedy.
94.5% is actually terrible.

If you have a prevalence of 10 in 1000, how do the numbers shake out?

Well, you test all 1,000. If we assume a 95% accuracy for false-positive and false negatives?

Of the 990 that you test that don't have the disease, the test will false state 50 do have the disease. Yikes!

And of the 10 that do have the disease? You'll miss 1 of them.