Characterizing The Types of Chronic Coughers
Chronic cough is any cough that has lasted for longer than eight weeks.
The most frequent causes of chronic cough include stomach acid reflux, postnasal drip, and asthma. It also happens that often chronic coughers do not have an identifiable underlying cause for their cough. Increased cough sensitization and a neurogenic origin have been reasoned for such states of chronic cough.
It becomes paramount in these cases to improve the quality of life for those living with a chronic cough. To do so first requires categorizing coughs within their various phenotypes to discern an appropriate management course.
Understanding Patient Perspectives on Chronic Cough
During the clinical presentation for a chronic cough, patients relay information they believe to be relevant to the cause of their cough. Often it is the documentation of a recent respiratory infection or allergic reaction, which are known causes of a cough. However, there are many causes, such as gastroesophageal reflux and its symptoms, which patients may fail to document when recording their cough.
Additionally, changes in the environment such as the sudden transition to a polluted city or occupational exposure are often overlooked. While such causes often take years to deteriorate lung function, an initial indication of the respiratory impact is the development of a nagging cough.
During the clinical presentation, it is crucial to discuss symptoms and the cough’s onset. Often coughs that persist following a bout of evident infection can be labeled as a post-infectious cough. In such cases, coughs are often the final lingering sign of a previous infection.
Relaying that coughs occur after heavy meals and more prominently during the night while the patient is sleeping should prompt investigation for stomach acid reflux.
Additionally, allergen exposure and understanding the medical history of hypersensitivity can also provide insight into chronic coughs.
Patients who document non-refreshing sleep, and daytime fatigue along with their chronic cough should be investigated for obstructive sleep apnea. While it may seem unlikely as a cause, especially for the patients who present with chronic cough, tracking such symptoms becomes vital in categorizing chronic cough phenotypes.
How Are the Different Types of Chronic Cough Phenotypes Distributed?
Studies have documented chronic coughs as prominently recorded among female patients. A primary reason for this is the higher likelihood of women reporting symptoms due to their related concerns, such as leaking of urine in high-pressure situations such as coughing.
Among chronic coughers, the most frequent phenotype is of the smoker. Current smokers, who document a history of more than 20 pack years of smoking (one pack year equates to 7300 cigarettes), frequently present with chronic nagging cough within the latter parts of their smoking years. Additionally, the cough variant is dry, with sputum production more prominent in the mornings. Patients who document having a history of cigarette smoking but have stopped note a decrease in chronic cough with time.
Outside of smokers, patients can then be categorized in the following phenotypes:
- Upper airway cough syndrome
- Lower airway cough syndrome
- Gastroesophageal reflux disorder
- Others (notable mentions include drugs, OSA, and multifactorial coughs)
- Idiopathic chronic cough
Upper airway cough syndrome (UACS) widely categorizes causes that result in a post-nasal drip. Pharyngitis, allergens, rhinitis, and anatomic disruptions (deviated septum) could result in a post nasal drip. Inflammatory changes to the sensory cough fibers due to persistent exposure as well as a recurrent cough form a feedback loop of increased cough frequency over time.
The primary phenotypes characterized as lower airway cough syndrome (LACS) include those who have asthma variant cough, chronic obstructive lung disease (COPD), or eosinophilic bronchitis. For both asthma and eosinophilic bronchitis, there is a chronic state of airway inflammation which results in coughing due to constantly agitated cough receptors. However, COPD conditions result in airways with limited capacity and recurrent bouts of hyperreactivity when exposed to aggravators. Most coughs among this variety are also of a dry and persistent variant.
Constant gastroesophageal reflux of stomach acid (GERD) results in the aggravation of the afferent cough fibers, especially with prolonged exposure at night. Patients can additionally present with an unusual taste in their mouth, chest discomfort, and dental erosions. A key facet to diagnosis is the repetitive appearance of symptoms when patients lie down or following the consumption of a large meal. Those who have GERD-induced cough, also have been observed to have lower cough thresholds and higher levels of mast cells and substance P, which are known to contribute to lingering chronic coughs.
Drug-induced coughs are often easier to assign a cause once thorough history is taken. The primary chronic cough phenotype under drug-induced cough is for patients taking ACE inhibitors. Currently, these drugs are the first-line options in the management of hypertension, which is one of the most frequently diagnosed lifestyle diseases. Cough can appear within hours of the initial dose or following months of drug use. This makes it crucial to reconsider ACE inhibitor use among patients who present with a chronic cough.
Finally, about 20% of chronic coughers have an unexplained source of their cough. Extensive investigation and even standard treatment trials fail to improve the quality of life for these patients, adding to long-term frustration. Often due to the failure of standard therapeutic regimes, alternative therapies such as speech therapy have proven to have some benefits in managing idiopathic chronic cough.
Could Automated Cough Tracking Help With Unidentified Chronic Cough Phenotypes?
To characterize coughs into their phenotypes, drawing a timeline and mapping out the evolution of the cough becomes vital. Within a clinical setting, it becomes difficult to visualize a cough a patient describes, especially if the sign doesn’t present itself during the examination. Additionally, with coughs related to GERD or other medical processes, symptoms such as fever, nighttime coughing, heartburn, and dyspnea play a key role in characterizing a cough.
For this, digital tracking tools play a critical role in narrowing down the cough phenotypes. Automated cough tracking devices, such as smartphone tracking apps, are capable of providing continuous cough monitoring. Since such devices, often within phones or smartwatches, are always with the individual, coughs are rarely missed. Changes in frequency and amplitude at different times of the day can also be documented. Cough tracking also eliminates patient or even recorder bias, as all sounds are tracked and only classified as cough or not-cough after recording.
Additionally, smart devices are also capable of recording external factors, such as the environment or medications, which could impact the appearance of a cough. Patients can log symptoms they experience even before a cough presents itself. This data proves useful when analyzing the trajectory of a chronic cough, making it easier to establish its phenotype. Thus also providing additional dimensions for idiopathic coughs, enabling possible diagnosis and management options.
The end goal for cough tracking is to improve management options, heighten chronic cougher’s quality of life and enable a more personalized healthcare approach.
Conclusion
Characterizing chronic phenotypes can be a difficult task, especially since chronic coughers present after a prolonged period. At this point, initial symptoms and the evolution of the cough with time make diagnosis a slightly tedious task, especially in cases of idiopathic or multifactorial variants of chronic cough.
Hyfe enables chronic coughers to have more input into their journey with their cough. The data they collect on their cough presents a unique insight for healthcare professionals to personalize their management to improve their quality of life. Continuous monitoring can also prevent the neglect of symptoms from both the patient and medical professional point of view.
As a healthcare professional, Hyfe looks forward to understanding how you characterize various cough phenotypes you encounter within your professional practice. Your feedback assists us with improving chronic cough diagnosis and management.
