Is Your Chronic Cough an Unwelcome House Guest?

Some things may be enjoyable in moderation, but strong perfume, group texts, houseguests,  and coughing lose their appeal when they persist. Coughing is a very useful, protective reflex. With a normal cough, the fast gush of air clears the airway of extra phlegm, water, or other particles. This is called a productive cough because the cough “produces” mucus you can expel. When you have mucus or food stuck in your throat, a good cough can get it out and save your life. When the cough happens in the absence of something in the throat or lungs, it is instead unproductive and can be annoying. When an unproductive cough lasts for several days it can be frustrating and painful. When it happens for several months, then you really have a problem. A problem called chronic cough.

Chronic cough is a non-productive cough that is pathological (disrupting normal body functions), and lasts more than 8 weeks. [In children, the criteria, causes, and prevalence, are very different; this article will only be discussing chronic cough in adults.] Chronic cough can last for months, years, or even decades. It is a widespread condition affecting around 10% of the global population and a slightly higher proportion in America. Most sufferers are female and the highest rates are in people 40-70 years old. Chronic cough may be related to other diseases, such as chronic obstructive pulmonary disease (COPD), asthma, sinus problems, gastroesophageal reflux disease (GERD), or pulmonary fibrosis. Additional risks include other respiratory infections, post-nasal drip, air pollution exposure, and smoking, which increases the chances of developing chronic cough by 300%.

Most people can cough on command, but it’s much harder to not cough when you feel like you have to. The throat has lots of nerves which sense the environment in the airway and send signals to the brainstem and upper brain areas. When a foreign or dangerous particle - like mucus or chili powder - enters the airway, special nerves sense these irritations and tell you to cough. Mucus and chili powder, however, run through different types of nerves, called fibers. Mucus is detected by A-delta fibers, which are very fast and detect acid and mechanical stimulation (solid things that move the nerves, like food). These are critical to prevent choking, and can be activated even in unconscious animals. Other particulate chemicals and irritants, like chili powder, activate C-fibers. These are slower and receptive to many different types of chemicals and irritants. The underlying cause of chronic cough is thought to be increased sensitivity of these nerves, which makes them send the cough signal all the time. It’s like being in a group text when everyone is talking; there is just too much noise, and you can’t leave the group or silence the notifications. The exact causes of cough sensory nerve hypersensitivity is unknown, and likely varies from person to person, though nerve inflammation may play a role.

There are many treatments and medications for cough, but many have limited evidence showing effectiveness for chronic cough. Non-pharmaceutical approaches include physiotherapy and speech therapy, and may be recommended in some cases, but few controlled studies have evaluated these for chronic cough. Treating any underlying conditions, like COPD, GERD, or asthma, is an obvious goal if possible. Beyond this, medicines to treat chronic cough must balance side effects with effectiveness. Over-the-counter medicines like antihistamines, dextromethorphan (Robitussin), and guaifenesin generally have low effectiveness for chronic cough (or the patient would have solved the issue!) When over-the-counter medicines fail, many people turn to prescriptions. Opioids and gabapentin target specific receptors on nerves, but those receptors are found all over the body and in the brain, leading to possible widespread side effects, including dependency on opioids. Other prescriptions, like benzonatate, target A-delta fibers, making dosing errors dangerous. In addition, many patients have tried some or all of these without relief and need new treatments. Clinical trials are underway for new medicines that are specific to receptors found on the C-fibers, helping tone them down while keeping the choke-preventing A-delta fibers functioning properly. With the help of clinical trial volunteers, patients may be able to kick chronic cough to the curb, just like that guest who stays long after the party is over.

Staff Writer / Editor Benton Lowey-Ball, BS, BFA

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Dicpinigaitis, P. V., Morice, A. H., Birring, S. S., McGarvey, L., Smith, J. A., Canning, B. J., & Page, C. P. (2014). Antitussive drugs—past, present, and future. Pharmacological reviews, 66(2), 468-512. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11060423/

Chung, K. F., McGarvey, L., Song, W. J., Chang, A. B., Lai, K., Canning, B. J., ... & Mazzone, S. B. (2022). Cough hypersensitivity and chronic cough. Nature Reviews Disease Primers, 8(1), 45. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9244241/

Morice, A., Dicpinigaitis, P., McGarvey, L., & Birring, S. S. (2021). Chronic cough: new insights and future prospects. European Respiratory Review, 30(162). https://err.ersjournals.com/content/30/162/210127

Morice, A. H., Jakes, A. D., Faruqi, S., Birring, S. S., McGarvey, L., Canning, B., ... & Dicpinigaitis, P. (2014). A worldwide survey of chronic cough: a manifestation of enhanced somatosensory response. European Respiratory Journal, 44(5), 1149-1155. https://erj.ersjournals.com/content/44/5/1149.short

Visca, D., Beghè, B., Fabbri, L. M., Papi, A., & Spanevello, A. (2020). Management of chronic refractory cough in adults. European Journal of Internal Medicine, 81, 15-21. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7501523/