Methods: A systematic literature review was conducted for the epidemiological studies that reported the prevalence of chronic cough in general adult populations, which were published in the peer-reviewed journals during the years 1980 to 2013. The operational characteristics of the most common definition were examined by meta-analyses of the male-to-female ratio in chronic cough prevalence.
Results: The systematic review included 70 studies. The most common definition was cough ≥ 3 months (12-month prevalence) without specification of phlegm (n=50), which conflicts with the criteria in clinical guidelines of cough ≥ 8 weeks.
Meta-analyses were conducted for the male-to-female ratio of chronic cough among 28 studies that reported sex-specific prevalence using the most common definition; however, the pooled male-to-female odds ratio was 1.26 (95% confidence interval 0.92–1.73) with significant heterogeneity (I2=96%, P<0.001), which was in contrast to previous clinical observations of female predominance in cough clinics.
Conclusions: This study indicates two important issues in defining chronic cough in further epidemiological studies. A conflict between epidemiological and clinical definitions in duration criteria needs to be resolved. Another unexpected difference in the gender preponderance between the community and clinics warrants clinical validation of the existing definition.