Alzheimer’s disease is the most common cause of dementia, affecting millions of people around the world.
It gradually destroys memory, thinking, and the ability to carry out everyday tasks. Although scientists have studied the disease for decades, many questions remain about exactly how it develops and how it can be slowed.
Two proteins have long been at the center of Alzheimer’s research.
One is beta-amyloid, which forms sticky plaques outside brain cells. The other is tau, which forms tangled fibers inside brain cells. Together, these abnormal proteins are believed to damage and eventually kill nerve cells.
In recent years, new medicines that remove amyloid plaques from the brain have changed the treatment of Alzheimer’s disease. These drugs, including lecanemab and donanemab, work by helping the immune system clear amyloid deposits.
Earlier medicines such as aducanumab showed that plaque removal was possible, but researchers have continued to debate whether removing amyloid also slows the underlying disease process and protects brain cells over the long term.
Now, a rare new study from researchers at the Perelman School of Medicine at the University of Pennsylvania provides some of the strongest human evidence yet that clearing amyloid plaques may also reduce the buildup of tau, the protein that is more closely linked to memory loss and brain cell damage.
The findings were presented at the 2026 Alzheimer’s Association International Conference and published at the same time in JAMA.
The study became possible because researchers were able to examine the brain of a man in his fifties who had participated in an Alzheimer’s clinical trial before his death. He had been diagnosed with mild cognitive impairment caused by Alzheimer’s disease and had received an anti-amyloid treatment during the study.
When scientists examined his brain under the microscope, they discovered something unusual. Some regions of the brain had been almost completely cleared of amyloid plaques, while nearby areas still contained large amounts of amyloid.
This created a unique opportunity to compare neighboring brain regions that had experienced different levels of treatment success.
The differences were striking.
Brain regions where amyloid had been successfully removed contained very little tau and showed far fewer signs of ongoing brain damage. In contrast, nearby areas where amyloid remained had much higher levels of tau tangles, greater inflammation, and more evidence of nerve cell injury.
Because both types of brain tissue came from the same person, the researchers could compare them without many of the differences that usually exist between separate patients.
The findings support the idea that amyloid buildup may occur first and help create conditions that allow tau to spread through the brain. If amyloid is removed early enough, the chain of events leading to widespread tau accumulation may be interrupted, potentially slowing the progression of Alzheimer’s disease.
The researchers believe this may help explain why the benefits of anti-amyloid drugs may become more noticeable over time. Most clinical trials have followed patients for about 18 months, but slowing the buildup of tau could produce larger benefits over several years as brain damage progresses more slowly.
Scientists also hope to understand why some brain regions were much better at clearing amyloid than others. Learning how to improve plaque removal throughout the brain could make future treatments even more effective.
Importantly, this research does not prove that amyloid removal alone can stop Alzheimer’s disease. It is based on a single patient, so larger studies are needed to confirm the findings. However, the case provides rare direct evidence from human brain tissue supporting one of the leading theories of Alzheimer’s disease.
The study also strengthens the case for treating Alzheimer’s disease as early as possible. Amyloid can begin building up many years before memory problems appear. If future studies show that removing amyloid before large amounts of tau develop can delay or prevent dementia, early diagnosis and treatment may become even more important.
Review and analysis: This study is highly valuable because opportunities to examine the brain of someone who received anti-amyloid therapy are extremely rare. Its greatest strength is the direct comparison of treated and untreated brain regions within the same individual.
However, because it involved only one patient, the results cannot establish cause and effect or predict how every patient will respond.
Even so, the findings provide compelling biological evidence that early and extensive amyloid removal may slow the downstream processes that drive Alzheimer’s disease and offer hope that earlier treatment could produce greater long-term benefits.
If you care about Alzheimer’s disease, please read studies about vitamin D deficiency linked to Alzheimer’s and dementia, and strawberries can be good defence against Alzheimer’s.
For more health information, please see recent studies about foods that reduce Alzheimer’s risk, and oral cannabis extract may help reduce Alzheimer’s symptoms.
Source: University of Pennsylvania Perelman School of Medicine.
