Allergy Asthma Immunol Res.  2019 Nov;11(6):871-884. 10.4168/aair.2019.11.6.871.

Age and Sex Distribution of Chinese Chronic Cough Patients and Their Relationship With Capsaicin Cough Sensitivity

• Lai K
• Long L
• Yi F
• Tang J
• Chen Z
• Chen F
• Zhou J
• Peng W
• Zhang L
• Li H
• Zhan W
• Chen R
• Luo W
• Chen Q
• Chung KF
• Zhong N

• KMID: 2459190
• DOI: http://doi.org/10.4168/aair.2019.11.6.871

Abstract

PURPOSE
An older female predominance has been reported among chronic cough patients in Western countries, which is considered to be associated with a higher cough sensitivity in females. However, the characteristics of Chinese chronic cough patients remain unclear. This study aimed to explore the age and sex distribution as well as their relationship with cough reflex sensitivity to capsaicin in Chinese chronic cough patients.
METHODS
We analyzed the demographic features of 1,882 consecutive chronic cough patients who attended our cough clinic in Guangzhou, China. Cough sensitivity to capsaicin, which was defined as the lowest concentration of capsaicin causing 5 coughs or more (C5), was measured in 539 of the 1,882 patients and 68 healthy volunteers.
RESULTS
The mean age of the patients was 43.0 ± 13.7 years and patients aged <50 years accounted for more than two-thirds of the study population. Around 87% of the patients were never-smokers. The proportion of females (51.5%) was almost equal to that of males (48.5%). The pattern of the age and sex distribution was consistently reflected within most common causes of chronic cough, while a female predominance was shown in patients with cough-variant asthma and patients aged ≥50 years. Female patients had higher cough sensitivity to capsaicin than male patients (log C5: 1.58 ± 0.84 vs. 2.04 ± 0.84 μmol/L, P = 0.001), and patients aged ≥50 years had higher cough sensitivity to capsaicin than patients aged <50 years.
CONCLUSIONS
In China, patients with chronic cough have a roughly equal sex distribution and a middle-aged predominance, irrespective of a higher cough sensitivity to capsaicin in females and older patients. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02591550

Keyword

Age distribution; capsaicin; cough; sex distribution; TRPV1 receptor

MeSH Terms

Age Distribution
Asian Continental Ancestry Group*
Asthma
Capsaicin*
China
Cough*
Female
Healthy Volunteers
Humans
Male
Reflex
Sex Distribution*
Capsaicin

Figure

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  Fig. 1 Algorithm for the management of patients with chronic cough. ACEI, angiotensin-converting enzyme inhibitor; FENO, fractional exhaled nitric oxide; UACS, upper airway cough syndrome; GERC, gastro-esophageal reflux related cough; CVA, cough-variant asthma; EB, eosinophilic bronchitis; SPT, skin prick test; IgE, immunoglobulin E; HRCT, high-resolution computed tomography; ECG, electrocardiogram; AC, atopic cough.

• 

  Fig. 2 Summary of screening procedures.

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  Fig. 3 Age and sex distribution of the whole study population. Percentage (%): ratios of the number of females or males to the total number of cough patients (n = 1,822).

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  Fig. 4 Sex distribution of different causes of chronic cough. Percentage (%): ratios of the number of females or males to the total cough patients (n = 1,822). CVA, cough-variant asthma; EB, eosinophilic bronchitis; GERC, gastro-esophageal reflux related cough; UACS, upper airway cough syndrome; AC, atopic cough.

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  Fig. 5 Age distribution of different causes of chronic cough. Percentage (%): ratios of the number of females or males to a specific cause. CVA, cough-variant asthma; EB, eosinophilic bronchitis; GERC, gastro-esophageal reflux related cough; UACS, upper airway cough syndrome; AC, atopic cough.

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  Fig. 6 Age and sex differences in cough reflex sensitivity measured as C5. The C5 values were logarithmically transformed (to base 10). Error bars indicate range, median and 25th and 75th percentiles. C5, the concentration of capsaicin causing 5 coughs or more.

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  Fig. 7 Cough reflex sensitivity measured as C5 in different causes of chronic cough. The C5 values were logarithmically transformed (to base 10). Error bars indicate range, median and 25th and 75th percentiles. C5, the concentration of capsaicin causing 5 coughs or more; CVA, cough-variant asthma; EB, eosinophilic bronchitis; GERC, gastro-esophageal reflux related cough; UACS, upper airway cough syndrome; AC, atopic cough; UC, unexplained chronic cough. *Females had significantly heightened cough reflex sensitivity compared to males.

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  Fig. 8 Cough reflex sensitivity measured as C5 in male patients with different smoking status. The C5 values were logarithmically transformed (to base 10). Error bars indicate range, median and 25th and 75th percentiles. C5, the concentration of capsaicin causing 5 coughs or more.

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