Links Between Nerves And Asthma
Is asthma getting on your nerves? Yeah! Mine too. And apparently, there may be some truth to this. A 19th century theory was asthma was a nervous disorder. This was disproved in the 1950s. But, our modern evidence seems to link nerves with asthma. So, does this vindicate 19th-century physicians? Here’s what to know
Is asthma all in your head?
Researchers now know asthma is the result of an abnormal immune response. Airways are chronically inflamed. Airways are hypersensitive to asthma triggers. Exposure to asthma triggers causes airway cells to over-respond. They treat these otherwise “innocuous” triggers as though they are harmful pathogens.
This triggers the abnormal immune response. Inflammatory chemicals are released. Some of these chemicals cause airway inflammation. Others recruit white blood cells (WBCs) to the area. The most common WBCs recruited are eosinophils. They are responsible for more aggressive airway inflammation. They are present in asthmatic airways during asthma attacks. They may stay present in airways of those with severe asthma.
Current efforts to treat asthma involve medicines to suppress this immune response. This is where corticosteroids fit in. They reduce the number of eosinophils. Other medicines reverse symptoms. This is where beta 2 adrenergics come into play. They relax airway smooth muscles. Together, these medicines open airways to make breathing easier.
Might asthma indeed be a nervous disorder?
That’s a possibility.1-2 Newer evidence suggests airway nerves may indeed cause asthma. They may cause that abnormal immune response.
This may explain why people with controlled asthma still have symptoms. These symptoms may be mild and easily controlled. But, symptoms still occur. This may be because airway nerves remain hypersensitive, despite this good control.
These nerves recognize asthma triggers. They send signals to the vagal ganglia. These signals are then sent to a part of the brain called the hypothalamus. A signal is returned from the hypothalamus. This is all part of your parasympathetic nervous system.
This signal tells airway epithelial cells to release some of their fluid. This causes airway inflammation. This signal tells goblet cells to release mucus. This causes mucus hypersecretion. This signal also tells smooth muscles cells to constrict. This causes bronchospasm. Together, these cause your typical asthma symptoms.1-2
One specific type of nerve is a sensory nerve. Like all cells, sensory nerve cells have receptors. The only type of such receptor is called TRPV1.
In one study in mice, the mice were given inactive neurons. They were also made to have an allergy to egg whites. When exposed to egg whites, all but one group of mice had allergy symptoms. The sensory neurons of the mice that did not get allergy symptoms had deactivated TRPV1 receptors.2
So, this may indicate a link between these sensory neurons and asthma. Perhaps further research in this area will lead to a new asthma remedy.
Will new technology prove the nervous theory?
This is possible. 3 Old technology allowed researchers to view 2D images of airway nerves. New technology allows them to see 3D images. Now, rather than just seeing surface nerves, they can see the entire nerve tree.
This new technology allowed researchers to compare nerves in asthmatic airways with nerves in non-asthmatic airways. What they concluded was that asthmatic airways have more airway nerves than non-asthmatic airways.
One theory explaining this is the presence of eosinophils in asthmatic airways. They suspect that eosinophils may irritate airway nerves, making them more sensitive. The brain may sense increased activity in the airways, triggering it to cause airway nerve cells to replicate. The result is an abnormal amount of these hypersensitive airway nerves.
This is one part of airway remodeling. This may be present in all asthmatic airways to some degree. Researchers also think it may play a role in asthma control. The more airway nerve cells in your airways the worse asthma control you may have. So, this phenomenon may also explain why some asthmatics develop severe asthma. 3
What to make of this?
Nineteenth-century physicians looked for links between nerves and asthma. But, what they lacked was the sophisticated tools available to today’s researchers. It is now believed as a fact that asthma is not a nervous disorder. But, there may still be links between nerves and asthma.
Reading about the impact of nerves is intense reading. It’s very complex. It’s getting on my last nerve. Still, this is another exciting area researchers are investigating. We’ll have to wait and see what it leads to.
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