Common causes of chronic cough

I believe everyone is familiar with the symptom of coughing. It can occur alone or it may be a symptom of other diseases. Chronic cough mainly refers to a cough that lasts for more than 8 weeks. There are many possible types of diseases. When this happens, finding out the cause in time will help us better deal with it. So, what are the common causes of chronic cough? Let’s take a look below.

1. Various nasal, pharyngeal and laryngeal diseases causing cough

Nasal diseases cause secretions to flow back into the back of the nose and throat, directly or indirectly stimulating cough receptors, leading to a syndrome with cough as the main symptom, which is called postnasal drip syndrome (PNDS). Since it is currently unclear whether it is caused by upper respiratory tract cough receptors, the 2006 American Cough Diagnosis and Treatment Guidelines recommend using upper airway cough syndrome (UACS) instead of PNDS.

UACS is one of the most common causes of chronic cough. In addition to nasal diseases, UACS is often related to throat diseases, such as allergic or non-allergic pharyngitis, laryngitis, throat neoplasms, chronic tonsillitis, etc. It is characterized by paroxysmal or persistent cough, mainly during the day, less coughing after falling asleep, postnasal drip and (or) a feeling of mucus adhesion on the posterior pharyngeal wall, a history of rhinitis, sinusitis, nasal polyps or chronic pharyngitis, and examination reveals mucus adhesion and a cobblestone-like appearance on the posterior pharyngeal wall. Chronic sinusitis imaging can show thickening of the sinus mucosa and the appearance of fluid levels in the sinuses. Coughing caused by the common cold may also be caused by irritation from secretions dripping from the back of the nose. Since the common cold is the most common illness in humans, postnasal drip syndrome is one of the most common causes of cough. In recent years, with climate change, worsening air pollution, patients taking cold medicines in combination and abusing antibiotics have led to an increasing number of cases of this disease.

2. Gastroesophageal reflux cough

It is a special type of gastroesophageal reflux disease (GERD) caused by the reflux of gastric acid and other gastric contents into the esophagus, resulting in cough as the prominent clinical manifestation. There are two views on the mechanism of extraesophageal manifestations of GERD. One is micro-aspiration, and the other is airway neurogenic inflammation caused by esophageal-bronchial reflex. Both can cause airway hyperresponsiveness. Typical reflux symptoms include heartburn (burning sensation behind the sternum), acid reflux, belching, etc. Some cases of cough caused by gastroesophageal reflux are accompanied by typical reflux symptoms, but for many patients, cough is the only symptom.

Cough is one of the most common extraesophageal symptoms of gastroesophageal reflux, followed by pharyngeal bulb sensation and/or pharyngeal foreign body sensation, burning pain in the throat, and hoarseness. The cough is mostly irritating and dry, but may also be a cough with phlegm. Most of the coughs are daytime coughs, and some are night coughs, often accompanied by digestive system symptoms such as heartburn, acid reflux, chest pain, and nausea. However, clinically, there are also many patients who have no reflux symptoms at all, and cough is their only clinical manifestation. 24-hour esophageal Ph monitoring can be used for diagnosis. The mechanism is unclear, but it may be related to the stimulation of cough receptors in the pharynx, larynx, and trachea by reflux. The use of antacids, prokinetic drugs, H2 receptor blockers, and proton pump inhibitors can quickly relieve symptoms. The treatment time is required to be more than 3 months, and it usually takes 2 to 4 weeks to show efficacy.

3. “Asthma” causes cough - cough variant asthma (CVA)

If the cough lasts for more than 2 months, the possibility of variant asthma should be considered. It is a special type of asthma in which cough is the only or main clinical manifestation. There are no obvious symptoms or signs such as wheezing and shortness of breath, but there is airway hyperresponsiveness. The diagnostic criteria are: chronic cough is often accompanied by obvious nocturnal irritating cough; positive bronchial provocation test or diurnal variation of peak expiratory flow (PEF)>20%; effective treatment with bronchodilators; exclusion of other causes of chronic cough.

4. Eosinophilic bronchitis (EB) causes cough

A nonasthmatic bronchitis characterized by eosinophilic infiltration of the airways. The clinical manifestations are not characteristic, mostly chronic irritating dry cough or coughing up a small amount of sputum, which may occur during the day or at night. Some patients are sensitive to fumes, dust, odors or cold air, which are often the triggers of coughing. There was an increase in eosinophils in the induced sputum, normal pulmonary ventilation function, no airway hyperresponsiveness, and normal daily variation of PEF. Sputum cytology examination showed that the proportion of eosinophils was ≥ 2.5%; other eosinophilic diseases were excluded; oral or inhaled corticosteroids were effective, while bronchodilators were ineffective. Before seeking medical treatment, most patients had a disease course of more than 3 months, or even several years. Some patients are related to inhaled allergens, such as dust mites, pollen, mushroom spores, etc., and some are related to occupational contact with chemical reagents or chemicals, such as rubber gloves, acrylates, etc. ICS is usually used for treatment, with beclomethasone dipropionate or other corticosteroids at an equivalent dose taken twice a day for more than 4 weeks. Dry powder inhaler is recommended; oral prednisone can be used in combination with initial treatment.

5. Allergic cough (AC)

There is no universally recognized standard at present, the following standards are for reference:

(1) Chronic cough, mostly irritating dry cough;

(2) Normal pulmonary ventilation function and negative bronchial provocation test;

(3) Having one of the following indications: ① History of allergic disease or contact with allergic substances; ② Positive allergen skin test; ③ Increased serum total IgE or specific IgE; ④ Increased cough sensitivity. Antihistamines are effective, and inhaled or short-term (3 to 7 days) oral corticosteroids can be added if necessary.

The above conditions are the most common causes of chronic cough. In addition to the above conditions, there are several other causes of cough. Many interstitial lung diseases often present dry cough as the main symptom in the early stages. In this case, pulmonary function tests can help with early detection. Drug-induced cough is common with ACEI and beta-blockers, with an incidence rate of around 15%. It occurs 24 hours or several months after taking the medicine, and is more common in women than in men, which may be related to the increased sensitivity of cough receptors. The symptoms will be relieved after stopping the medication for several days to 4 weeks. After excluding these factors, psychogenic cough may be considered, which is related to negative emotions such as tension, anxiety, and sadness. It is characterized by a barking or honking cough, an irritating dry cough, often accompanied by a clear throat sound. The cough has nothing to do with eating or drinking. An infectious cough can gradually develop into a psychogenic cough.