Objective: To investigate the changing patterns of the spectrum and frequency of causes for chronic cough, and to explore its clinical implications.
Methods: Nine hundred and forty patients consecutively referred to Department of Respiratory Medicine for evaluation of chronic cough between January 2004 and December 2008 were collected and divided into 5 groups by periods of 5 years. The causes of cough had been primarily evaluated according to a step-by-step protocol and confirmed by the specific therapy. The changes in spectrum and frequency of causes were retrospectively analyzed by chi2 test.
Results: The common causes of chronic cough were cough variant asthma (n = 437, 46%), upper airway cough syndrome/postnasal drip syndrome (n = 304, 32%), eosinophilic bronchitis (n = 87, 9%), gastroesophageal reflux-related chronic cough (n = 83, 9%), postinfectious cough (n = 60, 6%) and angiotensin-converting enzyme inhibitors-induced cough (n = 46, 5%) in descending order. There were significant differences in the distribution and frequency of etiologies when analyzed by year (chi2 = 60.6, P = 0.0001). During a 5-year period, chronic cough due to cough variant asthma increased from 44% to 51% (chi2 = 12.8, P = 0.010), upper airway cough syndrome/postnasal drip syndrome decreased from 49% to 29% (chi2 = 20.1, P = 0.001), and gastroesophageal reflux increased from 2% to 10% (chi2 = 17.6, P = 0.002). However, chronic cough associated with eosinophilic bronchitis, postinfection and angiotensin-converting enzyme inhibitors remained stable.
Conclusion: The common causes of chronic cough vary with time, which may have an impact on the strategy for the management of chronic cough.