Nose Itching Linked to Dementia Risk

Research conducted by scientists at Griffith University in Queensland, Australia, suggests a hypothetical link between the habit of nose-picking and an increased risk of developing Alzheimer’s disease and dementia.

The findings, published in Nature Scientific Reports, indicate that damaging the nasal mucosa through nose-picking may create a pathway for bacteria to enter the brain, potentially triggering the development of amyloid beta plaques.

The Pathway from Nose to Brain

The olfactory nerve provides a direct route from the nasal cavity to the brain. This pathway allows certain pathogens to bypass the blood-brain barrier, which typically prevents bacteria and other harmful substances from reaching brain tissue.

According to the study, the bacterium Chlamydia pneumoniae can travel up the olfactory nerve. In mice, researchers demonstrated that when the nasal epithelium—the thin tissue along the roof of the nasal cavity—was damaged, nerve infections became more severe.

The researchers suggest that nose-picking damages this nasal mucosa, making it easier for bacteria like C. Pneumoniae to reach the olfactory nerve and enter the brain.

Impact on Brain Pathology

Once these bacteria enter the brain, they can stimulate the deposition of amyloid beta protein. This protein is released in response to infections and forms plaques that are characteristic of Alzheimer’s disease.

Amyloid beta plaques are thought to be responsible for many of the core symptoms associated with Alzheimer’s, including unpredictable behavior, language problems and memory loss.

We’re the first to show that Chlamydia pneumoniae can go directly up the nose and into the brain where it can set off pathologies that look like Alzheimer’s disease

James St John, neuroscientist from Griffith University

Scientific Context and Limitations

While the findings provide a plausible mechanism for how environmental pathogens might contribute to dementia, scientists emphasize that the current research is based on tests in mice rather than humans.

The link is described as tenuous and hypothetical. However, the relevance to human health is supported by the fact that C. Pneumoniae can infect humans and has been discovered in the majority of human brains affected by late-onset dementia.

Alzheimer’s disease currently affects nearly 6 million people in the United States, with projections suggesting that number could reach 14 million by 2060. Understanding the pathways by which pathogens enter the brain remains a critical area of study for researchers attempting to solve the mystery of how the disease begins.

Further Implications

The study suggests that habits generally viewed as harmless or merely unpleasant, such as nose-picking, may carry risks that were previously unrecognized.

By identifying the olfactory nerve as a direct route for bacteria to bypass the blood-brain barrier, this research may improve the broader understanding of how external environmental factors and pathogens contribute to neurodegenerative diseases.