Scientists may have uncovered that Alzheimer's disease advances in the brain differently than prior studies have shown.
Alzheimer's disease, according to researchers from the University of Cambridge in England and Harvard Medical School in Massachusetts, does not start in a specific area of the brain before spreading to other areas.
They claim that by the time Alzheimer's disease manifests itself, it has already spread to many areas of the brain.
Researchers published their study, titled "In Vivo Rate-Determining Steps of Tau Seed Accumulation in Alzheimer's Disease," in the journal Science Advances.
A woman who has Alzheimer's disease looks at an old picture on March 18, 2011, in a retirement house in Angervilliers, eastern France.
Alzheimer's Disease Develops Differently Than Previously Thought
Georg Meisl, Ph.D., first author of the work and a researcher at Cambridge's Yusuf Hamied Department of Chemistry, said in a statement (via Eurekalert) that Alzheimer's disease develops similarly to many malignancies. According to Meisl, aggregates develop in one area of the brain and then spread across the rest of the brain.
When Alzheimer's disease first appears, however, researchers discovered that aggregates had already formed in numerous areas of the brain. As a result, Meisl pointed out that attempting to halt the disease's transmission between areas will have minimal effect.
The researchers used PET scans of persons living with Alzheimer's disease and postmortem brain tissues from patients who died from the condition to perform their research.
They studied the distribution of tau, a kind of protein linked to Alzheimer's disease.
Exponential Growth
Previous animal studies revealed that the aggregates start in one area and then move across the brain, similar to how cancer spreads.
While such spread may occur, according to the current study, it is not the primary cause of illness development.
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Meisl told AFP (via Bangkok Post) that the speed is controlled by the process of small pieces of aggregate multiplying throughout the brain.
An illustration from the COVID-19 pandemic is how travel prohibitions between countries failed to stop the virus from spreading since it was already reproducing within the countries attempting to keep it out.
The team also calculated how long it takes for the aggregates to double in size, about five years. According to Meisl, this is an "encouraging" result since it suggests that the brain's neurons are already capable of counteracting aggregates.
Alzheimer's disease is divided into six stages, each of which takes around 35 years to progress from stage three, when moderate symptoms first appear, to stage six, when the illness is most severe.
If aggregates double in five years, they will have increased 128-fold in 35 years. According to Meisl, this exponential development "explains why it takes so long for people to develop and then they tend to go worse very rapidly."
Stopping Alzheimer's Aggetates Might Help
As the world's population ages, dementia cases are expected to quadruple to more than 150 million by 2050. One of the reasons that drugs have failed is that they are provided too late when Alzheimer's disease has set in.
Plaques form and damage neurons, reducing grey and white matter, causing memory loss, personality changes, and disorientation.
Alzheimer's disease was formerly assumed to spread from one brain cell to another via synapses or connected circuits.
According to a report from Express, the disease appears spontaneously in several sites, which has implications for future therapies.
Co-senior author Professor Tuomas Knowles of Cambridge University said in the same report that stopping the reproduction of aggregates (also known as plaques) is a crucial discovery.
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