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alzheimer’s disease can be diagnosed years before symptoms appear, study says
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“changes occur in the brain between 10 and 20 years before the patient experiences any clear symptoms,” said oskar hansson, senior physician in neurology at skåne university hospital. getty
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a new study says that people with alzheimer’s disease can — and should — be diagnosed before they begin to exhibit symptoms based on the elevated presence of two problematic proteins in their brains.
the research, published in the journal nature medicine, concerns the activity of beta-amyloid (a protein that forms plaques in the brain) and tau (a protein that accumulates in the brain cells of alzheimer’s patients). historically, diagnosis for the disease has depended on elevated levels of both these proteins in addition to cognitive impairment.
“changes occur in the brain between 10 and 20 years before the patient experiences any clear symptoms and it is only when tau begins to spread that the nerve cells die and the person in question experiences the first cognitive problems,” said oskar hansson, senior physician in neurology at skåne university hospital and a professor at lund university. “this is why alzheimer’s is so difficult to diagnose in its early stages.”
after conducting a large international research study involving 1,325 participants from sweden, the u.s., the netherlands and australia, however, hansson said the process of diagnosis needs to change. his research, which involved using pet scans to visualize the presence of tau and beta-amyloid in the brains of participants, found that those with the two proteins faced 20 to 40 times the risk of developing alzheimer’s at follow-up a few years later compared to those with no biological changes.
“when both beta-amyloid and tau are present in the brain, it can no longer be considered a risk factor, but rather a diagnosis,” said rik ossenkoppele, first author of the study and senior researcher at lund university and amsterdam university medical center. “a pathologist who examines samples from a brain like this, would immediately diagnose the patient with alzheimer’s.”
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the study illustrates two schools of thought common among alzheimer’s researchers: those who believe the disease cannot be diagnosed until the emergence of cognitive impairment and those, like hansson and his team, who say diagnosis can and should be made purely based on biology and what they see happening in the brain.
“you can, for example, compare our results to prostate cancer,” said rik ossenkoppele, an associate professor in translational neuroscience. “if you perform a biopsy and find cancer cells, the diagnosis will be cancer, even if the person in question has not yet developed symptoms.”
the team of researchers has watched with interest as positive results have emerged from clinical trials into lecanemab, a drug currently being administered to alzheimer’s patients.
“if we can diagnose the disease before cognitive challenges appear, we may eventually be able to use the drug to slow down the disease at a very early stage,” hansson said. “in combination with physical activity and good nutrition, one would then have a greater chance of preventing or slowing future cognitive impairment.
“however, more research is needed before treatment can be recommended for people who have not yet developed memory loss.”
alzheimer’s disease is a chronic condition that results in the slow death of neurons, according to the alzheimer’s association. this process eventually produces symptoms of memory loss, difficulty thinking or changes in mood and behaviour. the disease is the most common cause of dementia in the world — accounting for 60 to 80 per cent of all cases — and more than 747,000 canadians are currently living with alzheimer’s or another form of dementia. roughly 65 per cent of people diagnosed with the disease after the age of 65 are women.
dave yasvinski is a writer with healthing.ca
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