The proposed mechanism is that damage to the inner tissue of the nose as a result of necrosis may open an easy path for certain types of bacteria, such as Chlamydia pneumoniae, to reach the brain, triggering an inflammatory response that resembles the signs of Alzheimer's disease.
It should be noted that these conclusions are based so far on research conducted on mice and have not yet been proven in humans, which necessitates caution in generalizing the results. Nevertheless, the study offers a new perspective that warrants further investigation into the origins of Alzheimer's disease, much of which remains unclear.
In experiments led by researchers at Griffith University in Australia, it was observed that Chlamydia pneumoniae, a bacterium known to cause pneumonia and often found in the brains of people with late-onset dementia, can travel via the olfactory nerve from the nose to the brain in mice. The severity of the infection increased significantly when the nasal epithelium was damaged, leading to the deposition of larger amounts of amyloid-beta protein, which is secreted in response to infection and whose plaques also accumulate in the brains of Alzheimer's patients.
Neuroscientist James St. John, who participated in the study, described the findings as "frightening for humans as well," noting that the bacteria reached the central nervous system of the mice in just 24 to 72 hours. This reinforces the hypothesis that the nose may be a fast track for bacteria and viruses to reach the brain.
Although the effects of this mechanism on humans are uncertain, and the role of amyloid-beta plaques in Alzheimer's disease remains controversial, the team emphasizes the importance of these promising research avenues. "We need to conduct this study in humans to confirm that the same pathway works in the same way," said St. John. He added that these bacteria are present in humans, but how they reach the brain is still unknown.
It is worth noting that nose picking is a very common habit, affecting up to 90% of people. While its motivations and potential harms are not entirely clear, this study calls for caution.
Researchers advise against picking or plucking nose hairs to protect the internal tissue, because damaging the nasal lining may increase the number of bacteria capable of ascending to the brain.
Future research will look to investigate whether the deposition of amyloid-beta protein represents a reversible immune response after the infection has cleared.
