A study published in 2022 found a tenuous but plausible link between picking your nose and increasing the risk of developing dementia.
In cases where scratching your nose damages internal tissues, critical species of bacteria have a clearer path to the brain, which responds to their presence in a way that resembles signs of Alzheimer’s disease.
There are plenty of caveats here, including that so far the supporting research is based on mice rather than humans, but the results certainly deserve further investigation – and could improve our understanding of how Alzheimer’s disease is triggered, which remains a mystery.
A team of researchers led by scientists at Griffith University in Australia carried out tests with a bacteria called Chlamydia pneumoniaewhich can infect humans and cause pneumonia.
The bacteria has was also discovered in the majority of human brains affected by late-onset dementia.
It has been shown that in mice, the bacteria can travel up the olfactory nerve (joining the nasal cavity and the brain). Additionally, when the nasal epithelium (the thin tissue along the roof of the nasal cavity) was damaged, nerve infections worsened.
This led the mouse brain to deposit more beta-amyloid protein, a protein released in response to infections. Patches (or clusters) of this protein are also found in significant concentrations in people with Alzheimer’s disease.
“We are the first to show that Chlamydia pneumoniae can go directly up the nose and into the brain where it can trigger pathologies that resemble Alzheimer’s disease. said neuroscientist James St John from Griffith University in Australia in October 2022, when the study was published.
“We’ve seen this happen in a mouse model, and the evidence is potentially frightening for humans as well.”
Scientists were surprised by how quickly C. pneumoniae took up residence in the central nervous system of mice, with infection occurring within 24 to 72 hours. It is believed that bacteria and virus think of the nose as a fast track to the brain.
Although it is not certain that the effects are the same in humans, or even that Beta-amyloid plaques are a cause of Alzheimer’s diseasenevertheless, it is important to follow promising leads in the fight to understand this common neurodegenerative disease.
“We need to do this study in humans and confirm whether the same pathway works in the same way,” says Saint John.
“This is research that has been proposed by many people, but has not yet been completed. What we know is that these same bacteria are present in humans, but we have not yet understand how they get there.”
Picking your nose isn’t exactly an uncommon thing. In fact, it’s possible up to 9 out of 10 people do it…not to mention a bunch of other species (some are a little more adept than others). Although the benefits are unclear, studies like this should make us think twice before choosing.
Future studies of the same processes in humans are planned – but until then, St John and colleagues suggest that picking your nose and plucking your nose hair is “not a good idea” due to potential damage this causes to the protective tissues of the nose.
One outstanding question the team will seek to answer is whether increased beta-amyloid protein deposits constitute a natural, healthy immune response that can be reversed when the infection is fought.
Alzheimer’s disease is an incredibly complex disease, as the a large number of studies inside and the many different angles scientists are trying to understand it – but each piece of research brings us one step closer to finding a way to stop it.
“Once you’re over 65, your risk factor increases, but we’re also looking at other causes because it’s not just age, but also environmental exposure. ” says Saint John.
“And we think bacteria and viruses are essential.”
The research was published in Scientific reports.
A version of this article was first published in November 2022.