Dementia is among the largest cause of disability in Australians aged over 65 and affects memory, intellect, rationality, social skills and everyday activities.
Alzheimer’s disease, which accounts for up to three quarters of all dementia cases, is generally diagnosed by testing memory and problem solving abilities, along with imaging tests to rule out other illnesses.
But new findings show that Alzheimer’s disease can be detected a decade or more before dementia symptoms appear, using imaging techniques such as MRIs and biomarkers from the brain.
Visiting dementia expert Professor John Breitner, who heads McGill University’s Centre for Studies on Prevention of Alzheimer’s Disease, explains how:
One of the biggest challenges in studying the biology of Alzheimer’s disease is the inaccessibility of the brain – we’re dealing with living beings so we can’t see their brains.
Instead, we use things called biomarkers. These aren’t symptoms but they allow us to identify Alzheimer’s activity in the brain before symptoms occur.
Some of the same chemicals present in the brains of people with Alzheimer’s disease are also present in the brains of people who are yet to show symptoms – and these chemicals are there for a decade or more.
Recent studies have been able to identify with some certainty, people who are on the road to developing Alzheimer’s disease.
In the future, we’ll probably be able to diagnose people in the community before they show symptoms – in other words, we’ll be able to identify people who are in the pre-symptomatic stages of Alzheimer’s disease.
This is important for two reasons.
First, if and when we come up with treatments or interventions that can slow the progress of the disease before symptoms occur, we’ll be able to identify the people for whom these treatments would be appropriate.
Second, it’s likely these very markers could be used in a quantitative way to measure the progress of the disease. If so, one could test interventions, such as medications, for their ability to stop or slow the disease in its pre-symptomatic state.
Slowing or stopping the disease before symptoms emerge is the key to preventing Alzheimer’s dementia.
How would you test for possible preventive treatments?
We’re studying a range of options and three look promising.
The first involves collecting spinal fluid in a process known as a spinal tap. This gives us access to the biochemistry of the spinal fluid, which is as close as we can get to the biochemistry of the living brain.
The second is Magnetic Resonance Imaging or MRI scans. These allow you to look at volumes and structural details in the brain and identify patterns of change over time. Functional MRI is even more interesting – it can actually measure brain activity in different regions.
We’re beginning to realise that people who have Alzheimer’s disease, and who are developing Alzheimer’s disease in the pre-symptomatic state, have altered patterns of brain activity that you can see with functional MRIs. This use of the technology is still in the experimental stage but it looks very promising.
The third is Positron Emission Tomography or PET imaging, which can measure the metabolic rate of different regions of the brain and detect patterns of change after a particular treatment.
These are the kinds of techniques that can be used to peer into the brain and look at activity in people who don’t have symptoms but who may be incubating the disease.
All of these techniques have potential and it’s not yet clear which will be the most sensitive and the most practical.
We’ve begun researching functional MRIs and spinal fluid tests because these are relatively easier and cost effective.
What types of treatments could be available in the next decade or so?
We’re looking at five different interventions, one of which – the non-steroidal anti-inflammatory drug naproxen – has already been shown to have an influence on biomarkers of Alzheimer’s disease.
But this is still preliminary research.
In studies of participants who are not demented but who may have pre-symptomatic Alzheimer’s disease, we’ve found naproxen treatment appears to reduce Alzheimer’s disease biomarkers, which indicate the ongoing progress of the disease.
This is one of the first times that investigators have been able to come up with at least preliminary evidence that interventions may actually alter the biology of the disease.
These studies are ongoing, and the next stage will be to test whether the interventions are also effective in preventing symptomatic Alzheimer’s dementia.
It’s too early to talk about the other four possible interventions because we don’t yet have enough data. But we’re hopeful at least some of them will work.
Do you expect biomarker tests to be rolled out as population-based screening for Alzheimer’s disease?
This would only be done if we’d developed a proven intervention that not only modified the biomarkers but also prevented the disease.
It’s very much analogous with heart disease – you can measure blood pressure, lipids and do various types of scans to find a predisposition to heart disease. Then you can treat these risk factors and typically reduce a person’s chances of developing heart attacks and strokes.
But in order for this to happen, we need to focus more energy into Alzheimer’s research.
The world spends less than 0.5% of its entire Alzheimer’s disease spending on research. That figure could be thought of as silly if it weren’t so unfortunate.
We’re facing a deluge of dementia. Governments have to get behind Alzheimer’s research and make sure it’s properly funded. Otherwise, we’re facing a catastrophe.