A team of Australian scientists has uncovered early evidence that damage inside the nose, potentially from habitual nose picking, may give harmful bacteria a direct route to the brain, triggering changes similar to those seen in Alzheimer’s disease.
The study, conducted by researchers at Griffith University and released in 2022, focused on Chlamydia pneumoniae, a bacterium capable of causing pneumonia in humans.
This same microbe has been detected in the majority of brains affected by late-onset dementia.
In laboratory experiments, mice were exposed to the bacteria through the nasal cavity.
The findings were striking: when the thin lining at the top of the nasal cavity, known as the nasal epithelium, was damaged, the bacteria travelled rapidly along the olfactory nerve into the brain.
Within 24 to 72 hours, infection had taken hold in the central nervous system.
The mice subsequently developed higher levels of amyloid-beta – a protein that accumulates in the brain as sticky clumps called plaques, commonly found in Alzheimer’s patients.
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Scientists believe this protein is released as part of the immune system’s response to infection, though it remains unclear whether the plaques are a cause or a symptom of the disease.
“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,” explained neuroscientist Professor James St John. “We saw this happen in a mouse model, and the evidence is potentially scary for humans as well.”
Although there is no direct proof that the same process occurs in people, the research underscores the potential risks of activities that injure nasal tissue, such as nose picking or plucking nose hair.
Habits could compromise the nose’s natural defences
According to St John, these habits could compromise the nose’s natural defences, making it easier for pathogens to reach the brain.
The next step for the team will be to investigate whether similar pathways exist in humans and whether amyloid-beta deposits caused by such infections are reversible once the infection is cleared.
With dementia cases rising worldwide, scientists are exploring not only age-related factors but also environmental triggers. “Once you get over 65 years old, your risk factor goes right up, but we’re looking at other causes as well, because it’s not just age – it is environmental exposure as well,” St John explained while noting that bacteria and viruses could be key players.”
Until more is known, researchers advise treating the inside of your nose with care – it may be a more important gateway to brain health than previously realised.
What you need to know about Alzheimer’s disease
Alzheimer’s disease is a progressive and irreversible neurological disorder that slowly diminishes memory, thinking abilities, and the capacity to perform everyday tasks, primarily affecting older adults. It stands as the most common cause of dementia.
According to the World Health Organisation (WHO) Alzheimer disease is the most common form of variety of diseases and injuries that affect the brain and may contribute to 60–70% of cases.
