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Alzheimer Disease: How Soon Would You Want To Know?


Cartoon of Alicia meeting a new doctor who wants to screen for Alzheimer disease on her 25th birthday



Have you been forgetful lately? Any difficulty concentrating? Trouble recalling names?

Answer “yes” to even one question like that, and there are some who want you to head to a clinic for memory screening. And it’s not because there is a good new treatment for dementia. If only there were.

Therapy for dementia remains a bleak landscape. And while we have a sense of some risk factors that could be modified (like smoking), there’s nothing solid enough to be an early prevention strategy, either.

Nevertheless, people are taking lessons from the cancer awareness-raising playbook to encourage and prime us towards believing we can prevent Alzheimer disease, and accept early – even very early – detection.

It seems to me we’re not prepared for this.

If we’re diagnosed with Alzheimer’s or any dementia, almost all of us would want to know it: somewhere around 90%, according to a recent study and systematic review (2014). But that’s not the same as wanting to be diagnosed early: there the numbers in favor drop steeply. A later systematic review concluded that “population screening for dementia may not be acceptable to either the general public or health care professionals”. (2015).

At the moment, the odds are that most of us won’t ever have to cross that bridge ourselves. And as people get generally healthier, the chances of a person at average risk getting Alzheimer dementia could fall, too. But a downside of early detection campaigns is a wave of false positives. They’re only worth it when the benefits outweigh the inevitable harms.

Early detection is intuitively compelling when faced with a dreadful, progressive disease. Get in and do something before it’s too late. But as I’ve discussed here before, hope can prevail over reason.

Appearances can be deceptive. When you start expanding the pool of people who are diagnosed, it means you are diluting the truly sick with many who were never going to get sick. That automatically seems to improve outcomes, feeding the impression that people are being helped.


Diagram of lead-time bias
Lead-time bias: How early detection shifting the diagnosis needle can lengthen “disease survival rate” without lengthening life.


In the case of dementia, timely diagnosis is what most of us seem to want. To know before not knowing has caused suffering around us, and while we still have time to make arrangements.

That’s not what’s driving the push to very early detection, though. The goal of very early detection is to find people so early in the development of the disease that they are not yet ill – and ultimately, about 25 years early, in mid-life, not old age. For those with a genetic susceptibility, possibly earlier than that.

But not only don’t we know if Alzheimer disease can be slowed down in its early stages, we don’t know yet how to tell who will get it. Even the best estimates are still quite vague. For people with mild cognitive impairment (MCI), roughly 20-40% will go on to dementia – but roughly 10-40% will return to normal cognition. Brain scans and blood or cerebrospinal fluid tests for dementia biomarkers aren’t accurate enough early on.

Neither the US Preventive Services Task Force nor the UK National Screening Committee recommend screening older adults for MCI or dementia. (Both have updates planned for 2018.) And most advocates of early detection are doing so to support research, not widespread screening.

But there’s strong advocacy to do it now – such as the “memory screening” clinics I mentioned earlier. And in the UK, another part of the National Health Service targets some groups of people for dementia for (including people with cardiovascular disease from the age of 60).


Image of etching
Schande (Shame) by Max Klinger


Margaret McCartney, a doctor in Glasgow and author of The Patient Paradox, wrote in the BMJ last year:

The rush to ‘early’ diagnosis has missed crucial dialogue. Earlier than what? Why? We should aim for timely, consensual diagnoses as part of a dialogue…A negative dementia screening result does not mean people do not have to plan for the future.

Early dementia diagnosis is more than a double-edged sword. People with dementia and their caregivers point to another concern: will a growing belief that the disease is preventable increase the burden of shame and stigma? That’s a reasonable concern, according to Claire Scodellaro and colleague. The stigma of Alzheimer collides with the stigma of aging – and both stigmas hit women harder.

According to Elizabeth Peel’s research, media coverage of Alzheimer disease and its prevention is heaping fuel on the stigma, and ushering in the belief in lifestyle changes that can “keep dementia at bay” – a precursor to victim-blaming.


Cartoon of Alicia thinking she needs another doctor


Keeping up this panic-blame-hype cycle serves some interests. But we have to turn it around.

In a risk assessment of the hazards of early detection, Steve Iliffe and colleague describe the diagnosis of dementia as “a portal into the world of ‘mental incapacity’ in which behavior becomes interpreted as a sign of the disease, and forgetfulness is itemized and monitored.”

We shouldn’t rush people headlong through it.

The push to re-define cognitive problems as “predementia” is part of a broader problem of expanding disease by creating “prediseases.” This variant, though, is one of the worst.


Close-up photo of a tree's bark with shadeContinued in a great conversation with links to literature on Alzheimer disease and personal experiences that followed when this was originally posted at Scientific American: “A particular stigma” Storify archived here.


This post was updated with additional research, including reviewing the status of national agency recommendations. An additional systematic review, not added to the post, looks at screening in primary care, found neither widespread adoption nor strong evidence in favor of screening (2017).

More from me on early detection in my post on The Prevention Illusion: A Tragedy in Five Parts.

The cartoons are my own (CC BY-NC-ND license): more at Statistically Funny.

More on Schande (Shame), an etching by Max Klinger (1857-1920). (Included here via Wikimedia Commons / the Google Art Project.)

The photo of the tree’s bark and shade is my own.

* The thoughts Hilda Bastian expresses here at Absolutely Maybe are personal, and do not necessarily reflect the views of the National Institutes of Health or the U.S. Department of Health and Human Services.


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