Alzheimer’s wreaks silent havoc in the brain long before symptoms appear, and now scientists have new clues about the dominant sequence of those changes—a possible window to intervene one day.
New discoveries in the diagnosis of Alzheimer’s disease PHOTO Shutterstock
A large study in China followed middle-aged and older adults for 20 years using regular brain scans, spinal taps and other tests, reports AP.
Compared with those who remained cognitively healthy, people who eventually developed the disease that steals their minds had higher levels of an Alzheimer’s-related protein in their spinal fluid 18 years before diagnosis, they reported Wednesday the researchers. Then, every few years after that, the study detected another so-called biomarker of brewing trouble.
The protein tangles and kills neurons
Scientists do not know exactly how Alzheimer’s disease is formed. An early hallmark is that sticky protein called beta-amyloid, which over time builds up into plaques and clogs the brain. Amyloid alone is not enough to affect memory – the brains of many healthy people harbor numerous plaques. An abnormal protein forms tangles that kill neurons.
The new research, published in the New England Journal of Medicine, provides a timeline of how these abnormalities accumulate.
The importance of the study “cannot be overstated,” said Dr. Richard Mayeux, an Alzheimer’s specialist at Columbia University who was not involved in the research.
“Knowing when these physiological events occur is critical” to testing new ways to treat and perhaps eventually even prevent Alzheimer’s disease, he wrote in an editorial.
The findings do not yet have practical implications.
Variants are being sought to delay the disease
More than 6 million Americans and millions more worldwide suffer from Alzheimer’s, the most common form of dementia. There is no cure. But last year, a drug called Leqembi became the first drug approved with clear evidence that it could slow the worsening of early-onset Alzheimer’s — albeit only for a few months.
It works by removing part of the amyloid protein. The approach is also being tested to see if it is possible to delay the onset of Alzheimer’s disease if people at high risk are treated before symptoms appear. Other drugs are being developed to target this protein.
Tracking silent changes in the brain is central to such research. Scientists already knew that in the rare, inherited forms that affect young people, a toxic form of amyloid begins to build up about two decades before symptoms appear, and at some point later, the abnormal protein kicks in.
Communication problems
The new findings show the order in which these biomarker changes occurred in more common Alzheimer’s disease in old age.
Researchers at the Beijing Neurological Disorders Innovation Center compared 648 people eventually diagnosed with Alzheimer’s and an equal number of people who remained healthy. The discovery of amyloid in future Alzheimer’s patients was the first, 18 years or 14 years before diagnosis, depending on the test used.
Differences were then detected in the level of the abnormal protein, followed by a marker of communication problems between neurons. A few years after that, differences in brain shrinkage and cognitive test scores between the two groups became apparent, the study found.
“The more we know about viable treatment targets for Alzheimer’s and when to address them, the better and faster we can develop new therapies and preventions,” said Claire Sexton, senior director of science programs at the Alzheimer’s Association She said blood tests are coming soon that promise to help.
2024-02-23 15:50:15
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