Need another reason not to pick your nose or aggressively pluck hairs that can sprout in there? A new study in mice offers some preliminary evidence that these habits might indirectly help increase your risk of developing Alzheimer’s disease.
The mouse study, published in Scientific Reports, found that Chlamydia pneumoniae bacteria can easily travel along a nerve running from the nasal cavity into the brain to infect the central nervous system in mice. When these bacteria invade the brain, it’s associated with a key marker of Alzheimer’s disease — the development of what’s known as amyloid beta protein deposits.
“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,” study coauthor James St John, PhD, head of the Clem Jones Centre for Neurobiology and Stem Cell Research at Griffith University in Brisbane, Australia, said in a statement.
“We saw this happen in a mouse model, and the evidence is potentially scary for humans as well,” Dr. St John said.
In mouse experiments, researchers contaminated the nasal passages in two sets of mice with C. pneumoniae bacteria. One set of mice had skin damage inside their nasal passages, while the other set of mice had healthy tissue there.
Within 72 hours, C. pneumoniae traveled to the brain in both sets of mice, the study found. But the bacteria appeared to invade the brain more easily and quickly — within 24 hours — in the mice with damaged tissue inside their nasal passages.
This suggests that protecting the skin inside the nose from damage might be one way to help limit the transmission of bacteria to the brain, St John said.
“Picking your nose [or] plucking the hairs from your nose is not a good idea,” St John said. “We don’t want to damage the inside of our nose, and picking and plucking can do that.
One limitation of the study is that C. pneumoniae moved into the brain much more rapidly than has been seen some previous experiments in mice. Earlier mouse studies found infection could take one week to three months. It’s possible infection happened more quickly in the new study because researchers exposed mice to higher concentrations of bacteria, the study team notes.
The biggest caveat to the study, however, is that outcomes in mice often don’t pan out in people.
While some research dating back more than a decade has found an association between C. pneumoniae and markers of Alzheimer’s disease — including some studies involving autopsies of people with Alzheimer’s disease — no studies to date have offered conclusive proof that C. pneumoniae directly causes the Alzheimer’s or that inhalation of this bacteria is responsible.
A wide range of infectious diseases can be transmitted through the air, causing illness when microbes are inhaled or come in contact with a mucus membrane such as the lining of the nose, according to the Centers for Disease Control and Prevention (CDC).
C. pneumoniae can cause pneumonia and other respiratory tract infections, the CDC notes. People can breathe airborne droplets contaminated with bacteria or touch their nose or mouth after coming in contact with droplets.
Symptoms typically begin three to four weeks after exposure, and include a runny or stuffy nose, fatigue, hoarseness or loss of voice, sore throat, cough, and headache, according to the CDC. People most at risk for these infections tend to live or work in crowded settings like schools, college dorms, military barracks, hospitals, prisons, or long-term care facilities, according to the CDC.
The best ways to prevent C. pneumoniae infection include common hygiene practices used for other respiratory diseases, like frequent hand-washing and resisting the urge to touch your eyes, nose, or mouth with unwashed hands.