Our nose does much more than help us smell the world around us. It also helps filter the air we breathe and acts as part of the body’s defense against germs.
Now, researchers have found evidence that the nose may also provide a direct path for certain bacteria to enter the brain.
A research team from Griffith University discovered that a common type of bacteria may travel from the nose into the brain. Their findings were published in the journal Scientific Reports. The work offers a new way of thinking about how infections could contribute to Alzheimer’s disease.
The scientists focused on Chlamydia pneumoniae, a bacterium best known for causing chest infections, sinus infections, and other respiratory illnesses. During the study, they found that this bacterium could move along the olfactory nerve, which carries smell signals from the nose to the brain.
The olfactory nerve is different from most other routes into the brain. Much of the brain is protected by the blood-brain barrier, which blocks many harmful substances. However, the olfactory nerve provides a more direct connection between the outside world and the brain.
To investigate this pathway, the researchers carried out experiments in mice. After placing the bacteria inside the nose, they found that it traveled through the olfactory nerve and reached the brain. Once there, it triggered the production of amyloid beta, a protein closely linked to Alzheimer’s disease.
Amyloid beta can build up into sticky clumps known as plaques. These plaques are believed to interfere with communication between brain cells and are one of the main features seen in the brains of people with Alzheimer’s disease. Scientists are still studying exactly how these plaques contribute to memory loss and other symptoms.
The researchers also examined what happens when the inside lining of the nose is damaged. Everyday habits such as picking the nose or pulling out nose hairs can injure this delicate tissue. The study suggests that damaged tissue may make it easier for bacteria to enter the body and possibly reach the brain.
Another important finding relates to the sense of smell. Many people with Alzheimer’s begin losing their sense of smell years before memory problems appear. Because of this, the researchers believe simple smell tests in older adults may one day help doctors detect early changes linked to the disease.
The current research was carried out in mice, so more studies are needed to learn whether the same process happens in people. The research team is now planning human studies to investigate whether bacteria can follow the same pathway into the human brain.
If future studies confirm these findings, doctors may eventually develop new ways to prevent or treat Alzheimer’s by targeting infections in the nose before they spread. Until then, looking after nasal health by avoiding unnecessary injury to the inside of the nose may be a sensible precaution. The study was led by Professor James St John and published in Scientific Reports.
If you care about Alzheimer’s, please read studies about the likely cause of Alzheimer’s disease , and new non-drug treatment that could help prevent Alzheimer’s.
For more health information, please see recent studies about diet that may help prevent Alzheimer’s, and results showing some dementia cases could be prevented by changing these 12 things.
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