Does picking your nose really increase your risk of dementia? Dementia researcher Joyce Siette in Australia take a closer look at a strange new study.
A 2022 study about a bacteria called C. pneumoniae, which is found in the nasal cavity and is association with deposits of Alzheimer’s biomarker beta-amyloid proteins in the brain, sounded alarms about the risks of a surprising — and surprisingly common — risk factor: nose-picking.
As one researcher pointed out in a blind peer review of the below write-up by dementia researcher Joyce Siette, nose picking is a common practice for humans of all ages. In fact, nine in 10 people admit doing it. At the same time, by the age of 20, research shows that about 50 percent of people have traces of C. pneumoniae in their blood — and that percentage rises with age.
Media spin around the C. pneumoniae study linked the two: nose-picking, and this scary bacteria. But the study was done in mice — not in humans. And as researchers know all too well when it comes to dementia and Alzheimer’s research, animal studies — especially mouse studies — rarely translate to humans.
A study review by Joyce Siette, a research fellow studying dementia at Australia’s Western Sydney University
No matter your age, we all pick our nose. However, if gripping headlines around the world are a sign, this habit could increase your risk of Alzheimer’s disease, the most common form of dementia.
One international news report said: ‘SCARY EVIDENCE’ How a common habit could increase your risk of Alzheimer’s and dementia. Another ran with: Alzheimer’s disease risk increased by picking your nose and plucking hair, warns study. An Australian news article couldn’t resist a pun: Could picking your nose lead to dementia? Australian researchers are digging into it.
Yet if we look at the research study behind these news reports, we may not need to be so concerned. The evidence connecting nose picking with the risk of dementia is still rather inconclusive.
What prompted these headlines?
Queensland researchers published their study back in February 2022 in the journal Scientific Reports.
However, the results were not widely reported in the media until about eight months later, following a media release from Griffith University in late October. The media release had a similar headline to the multiple news articles that followed: New research suggests nose picking could increase risk for Alzheimer’s and dementia.
The media release clearly stated the research was conducted in mice, not humans. But it did quote a researcher who described the evidence as “potentially scary” for humans too.
What the study did
The researchers wanted to learn more about the role of Chlamydia pneumoniae bacteria and Alzheimer’s disease. These bacteria have been found in brains of people with Alzheimer’s, although the studies were completed more than 15 years ago.
This bacteria species can cause respiratory infections such as pneumonia. It’s not to be confused with the chlamydia species that causes sexually transmitted infections (that’s C. trachomatis).
The researchers were interested in where C. pneumoniae went, how quickly it travelled from the nose to the brain, and whether the bacteria would create a hallmark of Alzheimer’s disease found in brain tissue, the amyloid β protein.
So they conducted a small study in mice.
The researchers injected C. pneumoniae into the noses of some mice and compared their results to other mice that received a dose of salty water instead.
They then waited one, three, seven or 28 days before euthanising the animals and examined what was going on in their brains.
What the study found
Not surprisingly, the researchers detected more bacteria in the part of the brain closest to the nose in mice that received the infectious dose. This was the olfactory brain region (involved in the sense of smell).
Mice that had the bacteria injected into their noses also had clusters of the amyloid β protein around the bacteria.
Mice that didn’t receive the dose also had the protein present in their brains, but it was more spread out. The researchers didn’t compare which mice had more or less of the protein.
Finally, the researchers found that gene profiles related to Alzheimer’s disease were more abundant in mice 28 days after infection compared with seven days after infection.
How should we interpret the results?
The study doesn’t actually mention nose-picking or plucking nose hairs. But the media release quoted one of the researchers saying this was not a good idea as this could damage the nose: “If you damage the lining of the nose, you can increase how many bacteria can go up into your brain.”
The media release suggested you could protect your nose (by not picking) and so lower your risk of Alzheimer’s disease. Again, this was not mentioned in the study itself.
At best the study results suggest infection with C. pneuomoniae can spread rapidly to the brain – in mice.
Until we have more definitive, robust studies in humans, I’d say the link between nose picking and dementia risk remains low.