Alzheimer’s disease is often linked with memory loss, but the earliest signs can be much more subtle. One of the first changes many people experience is a reduced ability to smell.
This may seem like a small issue, but it can be an early signal that something is happening in the brain.
For many years, researchers have observed this pattern but did not fully understand why it happens. A new study has now provided important answers.
The research was led by Professor Moon Cheil at the Daegu Gyeongbuk Institute of Science and Technology, together with a team from Maastricht University. The results were published in Alzheimer’s & Dementia.
Alzheimer’s disease develops when harmful substances build up in the brain. Two key proteins are involved. One is amyloid beta, which forms sticky plaques outside brain cells. The other is tau, which forms tangled fibers inside the cells. These changes slowly damage brain cells and interfere with normal brain function.
Earlier studies had shown that these proteins appear first in the parts of the brain linked to smell. These areas include the olfactory bulb and the olfactory cortex. However, scientists did not know how the brain’s defense system reacts in these regions during the early stages of the disease.
To explore this, the research team examined brain samples from people at different stages of health. Some had no signs of disease, while others had early memory problems or Alzheimer’s disease. By comparing these samples, the team could see how changes developed over time.
The findings showed that harmful proteins increased as the disease progressed, especially in the smell-related regions of the brain. This confirmed that these areas are among the first to be affected.
A key discovery was that the brain’s immune response is not the same in all regions. The brain uses special support cells to protect itself. Two important types are astrocytes and microglia.
In the olfactory cortex, astrocytes were more active in responding to damage. In the olfactory bulb, microglia played a stronger role. This shows that even within a connected system, the brain uses different strategies to respond to disease.
The researchers also found that a protein called apolipoprotein E builds up in these regions in all patients. This was seen even in people who do not carry a known genetic risk factor for Alzheimer’s. This suggests that the protein could be used as a general early marker of the disease.
Looking at the results, the study provides a clearer picture of how Alzheimer’s disease begins in the brain. It explains why smell loss happens early and shows that different brain regions react in different ways. This could be important for developing treatments that target specific areas of the brain.
At the same time, there are some limitations. The study is based on brain tissue collected after death, which cannot show how the disease changes moment by moment in living people. More studies are needed to confirm how these findings apply in real-life diagnosis and treatment.
Even so, the research offers strong evidence that the sense of smell is closely linked to early brain changes in Alzheimer’s disease. This means that simple tests of smell may one day help doctors detect the disease earlier.
Early detection is very important because it gives patients more time to plan care and possibly benefit from treatments that slow the disease. Understanding how different brain cells respond may also help scientists design better therapies.
In conclusion, this study provides an important step toward understanding Alzheimer’s disease. It shows that the brain’s response is complex and varies by region, and it highlights the potential of smell changes as an early warning sign. With further research, these insights could lead to better ways to detect and treat this condition.
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Source: Daegu Gyeongbuk Institute of Science and Technology.
