Getting rid of a chronic cough is harder than you think: ScienceAlert

When was the last time you walked into a public space and didn’t hear someone cough? After three years of hesitating with sound, it can be disconcerting to hear so many people coughing – and embarrassing if that’s you.

But take courage to know that you are not alone. A long-lasting cough after an upper respiratory infection is surprisingly common.

And unfortunately, with the increase in seasonal flu, COVID-19 and respiratory syncytial virus, or cases of RSV in the fall of 2022 and winter of 2023, there has been a lot of coughing lately.

Coughing is a common symptom of these types of respiratory infections, and coughing is a complaint that leads to around 30 million office visits every year. About 40% of them end up in a pulmonologist’s office like mine.

Given how ubiquitous the persistent cough is, you can assume that the medical profession has a long list of treatments that we know work. This, unfortunately, depends on why you are coughing.

But a cough after an upper respiratory infection usually goes away with time.

How does cough work

Doctors have long wondered why cough duration varies so much after a viral or bacterial upper respiratory tract infection. The answer likely lies in differences between people, such as the presence of a condition such as asthma or chronic bronchitis.

I see this same variability in my office: some patients develop a long-term cough, while others seem to start coughing much sooner, with no clear explanation.

Coughing occurs due to a complex process that begins with an electrical impulse between nerves in the airways, including the nose and throat.

There are two types of nerves that can trigger a cough in response to external stimuli: chemical receptors and mechanical ones called mechanoreceptors.

Chemical receptors respond to odors and vapors; they’re the reason people sometimes cough after breathing in hot peppers sizzling in a hot skillet. Mechanoreceptors respond to sensations from irritating substances such as dust.

When these nerves are activated, the throat closes and the pressure in the chest increases. This build-up of pressure leads to an explosion of air and mucus in the lungs at around 500 mph – a speed almost twice as fast as the fastest cars in the world.

Studies show that a viral infection alters the sensitivity of these same nerves. When you have a viral infection, the resulting inflammatory process produces a molecule called bradykinin that drives the urge to cough. And it is known that the virus itself can activate genetic changes that increase the sensitivity of these nerve pathways, which leads to more coughing.

But when the acute stage of the infection is over and you start to feel better, the body repairs the damage caused by inflammation in the airways and lungs. Through this process, the cough reflex also decreases. And the molecular processes that made you cough and sneeze more often settle down and return to their normal state – at least in most cases.

Unfortunately, in some people this process takes longer than in others.

Knowing how long is too long to cough

Doctors find it helpful to divide respiratory symptoms, such as coughing, into specific categories.

There are three main types of cough: acute, subacute and chronic. A hacking cough is what most people experience when they are sick with an active viral infection.

A subacute cough persists for three or more weeks after an upper respiratory illness. And a chronic cough is one that persists for more than 12 weeks. Chronic cough is most commonly caused by asthma, postnasal drip and, perhaps surprisingly to some, reflux.

Post-infectious cough is a variety of subacute cough and is the persistent cough that many people have after overcoming the respiratory infection. It can last for weeks or months and can progress to a chronic cough.

Because post-infectious cough is so common, doctors have worked for a long time to determine how many people have a cough that persists after other symptoms have disappeared.

These estimates vary across studies. A small study in Japan found that, of people with subacute and chronic coughs, 12% resulted from a respiratory tract infection.

When it comes to COVID-19, the best evidence to date shows that only 2.5% of people who contract it also develop a chronic cough after infection.

That number might sound small, but it translates to a lot of people coughing as the US has more than 280,000 new cases of COVID-19 a week since the beginning of February 2023.

The actual number, however, is unclear because studies looking at post-infectious cough are often small and only represent people who have contracted COVID-19 and come to the doctor’s office or on a telehealth visit for evaluation.

no simple solution

The American College of Chest Physicians and the European Respiratory Society have published guidelines to help clinicians deal with these uncertainties and the dearth of available data on the diagnosis and treatment of cough. Although the US guidelines were published in 2006, they still represent the best evidence available to clinicians and their patients.

About half of patients recover from the cough without any treatment. For those who don’t, the limited data available suggests that inhalers, steroids, narcotics, and certain over-the-counter medications may provide relief for some people.

In adults, evidence for the effectiveness of various treatments is mixed and limited. In my practice, I often prescribe a non-narcotic cough suppressant called benzonatate, sold under the brand name Tessalon Perles. It works by numbing the nerves in the lungs and airways, calming the cough reflex.

Data for treatments in children are also sparse, and studies have shown that over-the-counter cough suppressants and antihistamines were no more effective than placebo.

Home remedies can also play an important role for some patients. Many people swear by honey, and there is some limited supporting evidence behind its benefits.

One study showed that honey was more effective at relieving coughs than placebo over a three-day period.

When in doubt, ask a doctor

Being worried about a persistent cough is understandable – a quick Google search can turn up plenty of reasons to be concerned. While not a very satisfying answer, most coughs will eventually go away on their own.

However, if you lose weight quickly, cough up blood, have night sweats, or produce a lot of sputum, you should talk to your primary care physician. In rare cases, subacute and chronic coughing can be a sign of lung cancer or various forms of chronic lung disease.

If you’re simply nervous about it and want more information and advice, that’s reason enough to see your doctor. After all, coughing is the reason behind millions of office visits every year.The conversation

Kyle B. Enfield, Associate Professor of Medicine, University of Virginia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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