Alzheimer's could be diagnosed before symptoms emerge

A large study led by Lund University has shown that people with Alzheimer’s disease can now be identified before they experience any symptoms, and that it should be possible to predict who will deteriorate within the next few years. The study has been published in the journal Nature Medicine.

It has long been known that there are two proteins linked to Alzheimer’s — beta-amyloid, which forms plaques in the brain, and tau, which at a later stage accumulates inside brain cells. Elevated levels of these proteins in combination with cognitive impairment have previously formed the basis for diagnosing Alzheimer’s.

“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 Lund Professor Oskar Hansson. “This is why Alzheimer’s is so difficult to diagnose in its early stages.”

Hansson has now led a large international research study that was carried out with 1325 participants from Sweden, the US, the Netherlands and Australia. The participants did not have any cognitive impairment at the beginning of the study. By using PET scans, the presence of tau and amyloid in the participants’ brains could be visualised. The people in whom the two proteins were discovered were found to be at a 20–40 times higher risk of developing the disease at follow-up a few years later, compared to the participants who had 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, the first author of the study and a 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.”

Ossenkoppele explained that Alzheimer’s researchers belong to two schools of thought — those who believe that Alzheimer’s disease cannot be diagnosed until cognitive impairment begins and those who say that a diagnosis can be based purely on biology and what you can see in the brain.

“You can, for example, compare our results to prostate cancer,” he said. “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.”

Recently, positive results have emerged in clinical trials of a new drug against Alzheimer’s, Lecanemab, which has been evaluated in Alzheimer’s patients. Based on this, the study from Lund University is particularly interesting, say the researchers:

“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.”

Image credit: iStock.com/KatarzynaBialasiewicz

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