Screening for Alzheimer’s

What good can it do?

DRUG BUST by Alan Cassels

Test early, test often. That’s the mantra of doctors and disease groups who believe finding disease early is essential to a long and healthy life. Believing that an important aspect of staying healthy is eternal vigilance, they are promoting an ever-watchful eye, encouraging people to be scanned for a disease before it strikes them down.

Much of what passes for ‘preventative’ health nowadays involves screening programs of some type, such as mammography (for breast cancer) in women and PSA testing (for prostate cancer) in men. Even the innocuous lab work your doctor will periodically recommend involves screening, as he sends you to the lab to get your blood sugars and your cholesterol checked.

The allure of screening for disease is strong because it appeals to our need to be proactive and to ‘do something’ to keep ourselves healthy. I mean, why wouldn’t you want to be screened? It’s about being in control, isn’t it? Finding the disease when it is small and manageable allows you time to deal with it, such as having surgery or taking drugs to slow it down, stop it or prevent it from getting worse.

Intuitively, this is hard to argue with, yet the data on a whole range of screening programs leads me to believe that screening otherwise healthy people is embraced far too enthusiastically, often without an evidence base to support it and frequently causing harm. The screening might locate a ‘risk factor,’ which is associated with an increased future risk of developing some disease or another, but risk factors are rarely definitive. The problem, of course, is when our doctor tells us we have a ‘risk factor,’ we end up confusing it with the real disease and it – the risk factor, not the disease – becomes the focus of all our attention.

Screening healthy people makes sense, but only if it can conform to a few basic principles:

  • The test is simple and safe.
  • The ‘thing’ in question can be reliably found.
  • The thing they’re looking for can be found early enough to affect a cure.
  • Finding the thing can deliver a diagnosis that otherwise wouldn’t occur.
  • Our doctors can meaningfully do something about the disease indicated by the thing they’ve found.

Now, what to test? How about a test for getting old?

My reading of the position of the groups that work with Alzheimer’s patients indicates a powerful need to screen. The Alzheimer Society of Canada notes that cognitive impairment and dementia strike about 20 percent of elderly Canadians, yet less than one- quarter of the cases of Alzheimer’s disease in Canada is diagnosed and treated. The organization points out that, currently, there are about half a million Canadians living with dementia but, “by 2015, with baby boomers reaching the age of 65, the number of cases of dementia could jump by 50 percent.”

The problem is that, with the apparent tsunami of dementia heading our way, we know almost nothing about what causes it, how to prevent it or how to treat it. Researchers in the US recently analyzed 25 systematic reviews and 250 primary research studies in an attempt to determine the factors that cause Alzheimer’s or cognitive decline. Did they find definitive causes? Unfortunately not.

They found that if you had diabetes, possessed a certain kind of gene (APOE e4), had depression or were a smoker, these factors were ‘associated’ with an increased risk of developing Alzheimer’s. Factors that decreased your risk somewhat were keeping mentally and physically active, though the quality of the research evidence on this is poor.

Trying to detect Alzheimer’s disease early is based on the possibility of altering the course of the disease, but because there is no therapy proven to slow Alzheimer’s, it would seem to beg the question, “Why test healthy people for Alzheimer’s?”

The Alzheimer Society of Canada says that dementia-related issues, such as “motor vehicle accidents, medication errors and financial difficulties,” could be avoided by earlier diagnoses of the disease. It professes that finding Alzheimer’s early will help individuals have more time “to adjust to the diagnosis.” Sounds plausible yet I can’t help feeling that testing people for Alzheimer’s – possibly applying a “pre-Alzheimer’s” label 10 to 20 years before a person develops any symptoms, without having something substantial to give them – is a bit of a bust. To me, it’s like applying a cruel death sentence with no date as to when it will happen.

Part of my skepticism comes from the fact there are only a few instances where population screening of otherwise healthy people is worth the effort to find diseases before they can cause harm. This year, we have seen the reins seriously yanked back on mammography and PSA screening – the two screening programs that have undergone the most studies – because of the growing recognition of harm caused by false positive findings. And the fact you have to screen thousands of people over many years to prevent single deaths. The message is clear: unnecessary medical screening may not only waste your time and the health system’s money, but it may leave you worse off. More and more people will endure the anxiety, further testing and medical interventions, along with all the risks, costs and side effects these involve.

Screening for Alzheimer’s intersects with the common “aging tsunami” meme, which is often used to describe the expected bulge of aging boomers in Canada that will soon clog and bankrupt our cherished medical system. If Canada’s universal healthcare system is set to run aground and sink due to a boatload of aging and demented patients, we might accept all kinds of potential solutions, such as more screening, to avert the sinking. We might want access to more and better Alzheimer’s screening tools and a bigger public investment in detecting and avoiding this dreaded disease.

But using the “aging tsunami” meme ain’t gonna sell it. Why not? Because it rests on a falsity. A number of studies over the years estimate that the aging of the population doesn’t even add one percent a year to healthcare costs. What actually will threaten to sink the healthcare system is the fact that people of all ages are using more and more health services – many of them unproven, expensive and harmful, including more prescription drugs and screening tests – as well as many other services. Certainly, an older population will need places to live and people to look after them and communities will have to change and adapt to this. But a tsunami to healthcare? Nah.

In the energetic search to determine the risk for Alzheimer’s before it strikes, many scientists are exploring a handful of biomarkers, or biological signals, which they hope will show if a person is at risk of the disease before they have any symptoms. Finding these ‘risk factors’ involves some very invasive techniques, including CT scans of the brain (to identify changes in brain structure) and spinal taps (to identify protein fragments which may be linked to Alzheimer’s disease) as well as searching for specific types of genes which, again, may be ‘linked’ to Alzheimer’s. So far, these tests haven’t been definitive, and they have failed to pass the first two hurdles of an acceptable screening test. They are not simple, nor absolutely safe, nor very reliable.

Part of this is based on the need of scientists to rewrite the definition of Alzheimer’s, arguing it should be classified as a “clinical-biological syndrome.” One way to establish a diagnosis would be to base it not only on symptoms of dementia (forgetfulness, confusion and so on) but “biomarkers” such as a brain scan or an analysis of cerebrospinal fluid. If a person is already exhibiting mild signs of cognitive impairment, why go to the trouble to define Alzheimer’s in terms of a biomarker, you might ask.

Well, if you’ve got a biomarker, you can develop a drug (as groups such as Pfizer and Eli Lilly are trying to do) to work against the biomarker. In terms of treatment, things haven’t worked out that well on the drug front. Just recently, the drug giant Eli Lilly halted two clinical trials when its Alzheimer’s drugs, which were supposed to reduce plaque in the brain, made people more cognitively impaired and less able to look after themselves than those on placebo.

Some critics have said that, despite the recent drug trial failures, the real disappointment is that no drugs have been developed that address the root causes of Alzheimer’s, a definitively tough task, as no one really knows what those are. Some have said toxins in the environment may be at the root of the disease, but since you can’t patent a drug to reduce our exposure to environmental toxins, we’re unlikely to see much research funding go towards this. Like cancer or other diseases, you can be sure the bulk of the money will go toward treatment – and not prevention or cure – because that’s where the money is.

So back to the question: What about pre-Alzheimer’s? Should we try to find it and somehow stop it in its tracks if we can?

Alzheimer’s is certainly a dreadful disease that most of us would choose to avoid at almost any cost. As you lose mental function, your brain cells deteriorate and you become more confused and disoriented. You will soon stop recognizing people you’ve known and loved all your life. It’s terrible. But would being screened and finding out that in 10 or 20 years you might get it make it any less terrible?

I’m convinced that the drive to ‘screen’ people for Alzheimer’s is not being seriously questioned in the medical community because most people believe strongly in the “test early, test often” paradigm. That paradigm is not working out with mammography and prostate cancer screening and the question we should be asking is “Why should we expect anything different with Alzheimer’s?”

Alan Cassels is a drug policy researcher and author at the University of Victoria. He is currently writing a “pocket policy primer” on the ABCs of medical screening, A is for Alzheimer’s. Read his other writings

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