Coughs have always been viewed as a reflex to some allergen in the environment or hasty swallowing, or a sign of illness, but even healthy humans and many animals cough now and then. Following a global pandemic in part spread by respiratory droplets, coughing is being taken more seriously and cough research gained more popularity.

But what do we know about our coughs?

While many of us might associate a cough with an infection or allergy, some coughs are caused by an underlying condition affecting the heart or stomach. There are also coughs that stem from psychological processes. Many cough cases last longer than the duration of a specific condition and can continue beyond eight weeks, which is the clinical dividing line for a cough to be labeled as chronic.

We’ve collected some interesting cough facts and statistics to better understand this seemingly normal reflex.

Understanding the Science of Cough

  • Cough1 is the “violent expulsion of air from the lungs with a characteristic sound.
  • A cough reflex arc2 is formed by:
    • An afferent pathway, going in to your central nervous system, is formed by sensory nerves present within the epithelium of the upper respiratory tract;
    • This triggers the cough center present in the brain (specifically the upper brainstem and pons);;
    • An efferent pathway, going out from your central nervous system, is formed that travels through the phrenic, vagus, and spinal motor nerves to the muscles of the diaphragm, chest, and abdomen.
  • Coughing, on its own without other symptoms, can reduce a person’s quality of life. Other possible impacts of continuous coughing include:
    • Anxiety, depression, and other mood concerns3
    • Incontinence4
    • Sleep disturbances5

Basic Cough Statistics

Woman-cough-at-outdoor | Feature | Chronic Cough Negatively Impacts Quality of Life, Study Shows
  • Cough is one of the most common reasons people seek medical care (around 10% of visits to the emergency department are just for coughs).6
  • Infections of the upper respiratory tract and acute bronchitis account for 60% of the diagnosed cases7 presenting with acute cough.
  • Chronic cough, a cough lasting for more than eight weeks, affects 10% of the global population8.
  • The three most common causes of a chronic cough9 are:
  • While most coughs are non-threatening, a few coughs can be indications of underlying life-threatening conditions,10 such as cancer, pulmonary embolism, heart failure, or pneumonia.
  • Common medications can also be a source of a chronic cough, such as:
    • Blood pressure medications angiotensin-converting enzyme inhibitors (ACEIs)11 and angiotensin receptor blockers (ARBs)12
    • Nasal sprays13
    • GERD drug Omeprazole14
    • NSAIDs such as aspirin and ibuprofen, especially among asthmatics15
    • Statins16 to treat high cholesterol
    • Anti-rheumatic drug Leflunomide17
  • 90% of the cases of night-time coughing18 can be attributed to the same three causes mentioned above, plus ACE inhibitor therapy:
    • Gastroesophageal reflux disease (GERD)
    • Cough variant asthma
    • Upper airway cough syndrome 
  • Exercising can result in a cough, often seen among athletes. It occurs due to constriction of small airways (bronchi and bronchioles) and has a  5 – 20% prevalence19 in the general population.

How the Environment Affects Your Cough

How Ambient Air Pollution Affects Our Health placard | How Ambient Air Pollution Affects Our Health | feature
  • Worldwide, air pollution is a consistent cause of worsening coughs and respiratory health. It causes inflammation of the lungs and hyper-sensitivity to cough triggers.20 During the Beijing Olympics in 2008, traffic was deliberately restricted to reduce air pollution and a fall in reports of coughing and asthma was noted.21
  • Chronic cough is more widely reported by European and American populations than Asian ones.22 This showcases how health-seeking behavior differs in various parts of the world, such as whether to treat at home or go to a medical professional. Additionally, the type of medicine practices (for example, Western medicine or Chinese traditional medicine)23 affects the diagnosis and reporting rates.
  • Major cough-causing outdoor air pollutants24 particulate matter (from sources like car exhausts, industrial, factories, ash or soot from burning) and gases (such as nitrogen dioxide, ozone, and sulfur dioxide).
  • Chronic bronchitis, asthma, emphysema, chronic obstructive pulmonary disease (COPD), and lung cancer, frequent causees of chronic cough, are all linked to cigarette smoking.25
  • Burning biomass fuel (e.g., wood), for heating or cooking, without proper ventilation pollutes the air inside your home.26   Poor indoor air quality is particularly acute in places where cooking is done over wood and charcoal,27 but is also associated with natural gas stoves.28 This causes around 3 million deaths a year worldwide; 26% of these deaths29 resulted from lower respiratory tract infections and 23 % from COPD30 (both mentioned above as cause of chronic cough).
  • Inhaling various dusts at work, such as coal dust or asbestos, can lead to developing pneumoconiosis – this accounts for approximately 453,000 cases of lung disease31 yearly. 
    • 18.7% of cement workers32 stated that chronic cough was their primary complaint following long-term occupational exposure and a further 15.8% had developed asthma. Silica dust was their primary source causing occupational lung disease. 
    • A study on cotton mill workers in northern Benin recorded that 22 % of its 216 workers directly exposed to cotton fibers33 experienced a chronic cough lasting at least three months. 
    • Even if you do not develop pneumoconiosis, breathing in dust can cause chronic cough: a study conducted among 970 coal miners observed that 50.1% of them developed a non-pneumoconiosis chronic cough34 over time.
  • Coughing can also be caused “second-hand” – if a spouse of such a worker inhales dust and irritating particles from the worker’s hair or clothes, they can develop similar coughs and lung issues to the worker. This is frequently seen with spouses of asbestos workers.35

Effectiveness of Cough Treatments and Remedies

There is a plethora of cough treatments and remedies available. Here are some facts about them so you can choose effective options for yourself.

Medical Cough Treatments

  • Over-the-counter, non-prescriptive medications are the most commonly used methods to manage an acute cough.36
  • Dextromethorphan (sold under names including Buckleys Mixture, DayQuil Cough, and Babee Cof) is a frequently used cough suppressant. Studies have indicated a significant efficacy in cough suppression37 over placebo.
  • Guaifenesin is an expectorant, given for “wet” (productive or chesty) coughs to loosen and expel mucus. Guaifenesin has also been studied to reduce cough sensitivity,38 especially among those who have a cough due to an upper respiratory infection.
  • Antihistamines are frequently used to manage allergy symptoms, which can often include a cough. Certain types of antihistamines39 have specific cough-reducing effects. However, antihistamines, such as cetirizine, can also result in a dry cough as a side effect.
  • The use of inhaled corticosteroids to manage cough variant asthma can help reduce the progression rate to classic asthma by 30 to 40%.40
  • COPD cough is caused due to mucus accumulation in the respiratory tracts: 
    • Studies have been conducted to observe the effects of cough suppressants containing codeine41 and their effect on COPD cough but have not found it more effective than a placebo.
    • Medications such as prednisone42 and tiotropium43 reduce mucus secretion and are beneficial for COPD cough.
  • Several studies have highlighted a high prescription rate of antibiotics for the management of acute cough, whether it is caused by a bacterial infection or not:
    • Children presenting with an acute cough and diarrhea received antibiotics approximately 89% of the time44 in a study conducted in Northern Tanzania.
    • 32% of the antibiotics prescribed to children45 presenting at the emergency department in the US  between 2009 and 2014 were not developed for the conditions they were given for (they were not indicated for those cases).
    • There has been a rise in the prescription for antibiotics for adult cough in the United States, from 59% in 1980 to 70% in 1994.46
    • The antibiotics given47 to treat cough have frequently been tetracycline or amoxicillin, even when unjustified.
    • Additionally, antibiotics are sometimes taken without consulting a doctor and, in cases of viral infections with acute cough, result in no therapeutic effect (as antibiotics only work in bacterial infections), instead contributing to the huge burden of antimicrobial resistance.48
  • Speech and language therapy has been observed to have effective results in refractory chronic cough and other unexplained coughs:
    • Through cough suppression techniques, the coughing reflex is replaced49 with attempts to focus on breathing, swallowing, or other acoustic sounds.
    • Studies have shown a decrease in the urge to cough50 following regular practice with a speech-language therapist.

Cough Remedies

  • Literature reviews have highlighted that the use of honey can reduce severity and frequency51 of upper respiratory tract infections, such as a cough. 
  • Active components in ginger, such as gingerol, have been observed to facilitate airway muscle relaxation,52 which can assist with cough suppression, especially among asthmatics.
  • One study showed an increase in the number of coughing episodes53 among asthmatic adolescents who did not drink enough. This highlights the importance of remaining hydrated to reduce the frequency of coughing episodes.
  • Certain herbs have been observed to assist with improving cough frequency and providing relief from other upper respiratory symptoms:
    • Bromelain,54 an extract from the pineapple plant, has been studied to have anti-inflammatory properties that reduce symptoms such as cough in upper respiratory tract illnesses.
    • In a study with 749 participants, about 87.2% of individuals experiencing discomfort due to a cough experienced some relief when a thyme/ivy syrup was added55 to their treatment regimes.
    • Slippery elm56 has been observed to coat mucus membranes – this could reduce sensations that may trigger a cough. Its anti-inflammatory properties can reduce laryngeal irritation.
    • Cough syrups containing marshmallow root, ivy, thyme, and aniseed,57 have been studied to improve symptoms by almost 90% in patients who have chronic bronchitis and respiratory tract diseases.

Cough Research: Past, Present, and Future

three scientists are working together-feature-ca | Epidemiology: The Study of The Spread of Health-Related Events Within A Population | feature
  • Cough research is still in its infancy. Developments in cough research can help with both disease prognosis and monitoring recovery58 of specific respiratory diseases.
  • Current methods to assess and record cough for research59 include:
    • Cough visual analog scores
    • Health status questionnaires recording cough features
    • Measuring cough reflex sensitivity
    • Cough monitors and trackers
  • Studies60 have been conducted to check how automated cough counters are lacking in comparison to manual cough counting within research settings. Areas requiring more work for cough trackers include:
    • Detecting individual coughs within bouts of coughing
    • Differentiating cough from other sounds, such as speech 
    • Eliminating background noises
    • Developing the AI based on a wider variety of cough frequency from differing patient vocalizations

Breakthroughs in Cough Research

  • AI systems will become more efficient in detecting cough sounds61 as cough databases increase in size over time.
  • Short-duration (few hours–24h) cough monitoring can often miss important changes in cough frequency,62 therefore AI technologies allowing for seamless continuous cough monitoring is the vital to future efforts to understand and better treat cough.
  • Your the noise of your cough and its sound power63 are the two key facets that can be measured through an AI-powered cough tracker.
  • Recent studies show the involvement of chemical receptor P2X3 in the cough reflex. Newly developed drugs, which are pending FDA approval (gefapixant,64 sivopixant,65 and BLU593766), block these receptors to reduce cough frequency among those with unexplained and refractory chronic cough.
  • Research that collects audio data of coughs, once validated, could support and improve tuberculosis control programs67 – improving public health programs and TB care.

Cough and COVID-19 Statistics

The Covid-19 pandemic spread primarily through the dispersion of droplets containing the virus through expulsions such as coughs or sneezes.
  • A dry cough was noted as an initial symptom in about 60 – 70% of COVID-19-positive68 patients at the outset of the pandemic.
  • Cough was present 19% of the time69 among literature reviews recording long COVID-1970 symptoms.
  • A study indicated that SARS-CoV-2 may damage sensory nerves71 that are part of the cough reflex, leading to cough hypersensitivity,, a likely reason why it can produce a chronic cough after the primary infection clears.
  • Antitussive and expectorants72 are the primary methods used to tackle COVID-19 cough.
  • A study conducted in Iran73 showed the benefits of natural supplementation of ginger along with Echinacea in managing symptoms such as shortness of breath and cough for COVID-19 patients.

Conclusion

Your cough can speak volumes of the possible underlying changes occurring in your body. From food moving down your trachea to viral particles irritating your respiratory tract, almost anything can trigger a cough.

The duration, consistency, and features of your cough provide significant insight into its possible causes, such as whether you are coughing more at night or day. Simple details such as this can provide great information about what could be causing your cough.

For a persistent cough, consider checking in with your healthcare provider.


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