A study has established an interesting link between Alzheimer’s disease and nose picking. Alzheimer’s disease (AD) is the most common form of dementia, and the environment and genetics are thought to play a role in its development.
Research suggests the pathogens may also contribute to the development of Alzheimer’s disease, but the pathways by which they enter the brain were unclear until recently.
An Australian study found that a bacterium, Chlamydia pneumoniae, enters the brain through the olfactory nerve from the nose, leading to the development of beta-amyloid plaques characteristic of Alzheimer’s disease. The authors suggest that picking your nose damages the nasal lining, which makes it easier for bacteria to reach the olfactory nerve and enter the brain.
Picking your nose is a habit that is generally considered unpleasant, but harmless. However, research from Griffith University in Queensland, Australia, suggests that this activity may not be as risk-free as previously thought. The research, published in Nature Scientific Reports, shows that by damaging the nasal cavity of mice, bacteria can enter the brain through the olfactory nerve. Once in the brain, certain bacteria stimulate the deposition of beta-amyloid protein, which can lead to the development of Alzheimer’s disease. The beta-amyloid protein forms plaques that are thought to be responsible for many of the symptoms of AD, such as memory loss, language problems and unpredictable behavior.
Alzheimer’s disease currently affects nearly 1 million people in France.
From the nose to the brain: a direct route
The olfactory nerve leads directly from the nasal cavity to the brain. Bacteria that enter the olfactory nerve can therefore bypass the blood-brain barrier that usually prevents them from reaching the brain. The study, carried out on mice, showed that Chlamydia pneumoniae, a bacterium that causes respiratory tract infections, such as pneumonia, used this route to gain access to the central nervous system. Brain cells reacted to the invasion of C. pneumoniae by depositing amyloid beta protein. Beta-amyloid protein builds up in plaques that are a hallmark of Alzheimer’s disease.
Studies have already shown that Chlamydia pneumoniae is present in Alzheimer’s plaques in humans (using post-mortem analyses). However, it is unclear how the bacteria get there, and whether they cause AD pathologies or are simply associated with them. This work in mice shows that these same bacteria can quickly move up the olfactory nerve and initiate pathologies similar to AD.
The link between bacteria, viruses and brain disorders
This study adds to the results of several studies that have suggested a link between pathogens and dementia. In 2008, a study suggested that C. pneumoniae infection could trigger late-onset Alzheimer’s disease. Another study, performed in 2010, linked C. pneumoniae infection to the pathogenesis of Alzheimer’s disease, finding the simultaneous presence of C. pneumoniae, amyloid deposits and neurofibrillary tangles in the brain.
There are potentially many microorganisms that can contribute to the onset of AD. For example, the herpes simplex virus has been implicated in several studies. And it may take a combination of microbes and genetics. We all have bacteria/viruses in our brains, but not all of us have AD, so it may be a combination of microbes and genetics that lead to pathologies and symptoms.
It may also be a long and slow process. The researchers therefore do not believe that the presence of the bacteria in the brain means that you will have dementia next week. Rather, the bacteria triggers a slow progression of pathologies that can take decades before leading to symptoms. Viral contributions to Alzheimer’s disease provide an intriguing area of research to study this association, but to date no definitive causal relationship has been demonstrated, including in humans. Alzheimer’s disease is a complex disease with many contributing factors. And while we need to explore all avenues, it is likely that multiple causes contribute to the underlying biology of the disease.
The study in humans
This study showed that C. pneumoniae moved easily from the nose to the brain in mice, so the researchers are now extending their investigations to humans.
Human studies are going to be launched a study in Queensland, Australia. Researchers are recruiting people with early stages of late Alzheimer’s disease, then they will determine what bacteria are present in their noses and what genetic and protein changes occur.
The harmful effects of the nose pick
So, does picking your nose increase the risk of Alzheimer’s disease? Although research continues to establish a definite causal link, the habit of picking your nose may pose other health risks, including:
the introduction of viruses, bacteria and other contaminants into the nose,
the spread of bacteria and viruses from the nose on surfaces in the environment,
damage the tissues and structures inside the nose.
This damage and the introduction of pathogens may increase the risk of Alzheimer’s, as research to date indicates. Researchers advise avoiding picking your nose and plucking nose hair. If you damage the nasal lining, you increase the number of bacteria that can enter your brain. So, should we resist the urge to rip off those boogers? For researchers, this could be a good idea!