Asia is one of the most diverse and dynamic continents. Due to recent rapid industrialisation and urbanisation, morbidity patterns are likely to be diverse in Asian populations. Chronic cough is a disease condition resulting from host-environmental interactions, and is associated with a high global epidemiological burden. However, the underlying epidemiology remains unclear, particularly in Asia. We performed a literature search to identify peer-reviewed articles on chronic cough in community-based adult Asian populations that have been published between January 2000 and June 2015. In this review, we aim to examine the epidemiological characteristics and determinants of chronic cough in several geographical areas of Asia.
Adult ; Asia ; Asian Continental Ancestry Group ; Cough ; Epidemiology ; Humans ; Risk Factors

PURPOSE: Recent evidence suggests a global burden of chronic cough in general populations. However, the definitions vary greatly among epidemiological studies, and none have been validated for clinical relevance. We aimed to examine previous epidemiological definitions in detail and explore the operational characteristics. METHODS: A systematic review was conducted for epidemiological surveys that reported the prevalence of chronic cough in general adult populations during the years 1980 to 2013. A literature search was performed on Pubmed and Embase without language restriction. Epidemiological definitions for chronic cough were classified according to their components, such as cutoff duration. Meta-analyses were performed for the male-to-female ratio of chronic cough prevalence to explore operational characteristics of epidemiological definitions. RESULTS: A total of 70 studies were included in the systematic review. The most common epidemiological definition was identified as 'cough > or =3 months' duration without specification of phlegm (n=50); however, it conflicted with the cutoff duration in current clinical guidelines (cough > or =8 weeks). Meta-analyses were performed for the male-to-female ratio of chronic cough among 28 studies that reported sex-specific prevalence using the most common definition. 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 clinical observations of female predominance from specialist clinics. Subgroup analyses did not reverse the ratio or reduce the heterogeneity. CONCLUSIONS: This study identified major issues in defining chronic cough in future epidemiological studies. The conflict between epidemiological and clinical diagnostic criteria needs to be resolved. The unexpected difference in the gender predominance between the community and clinics warrants further studies. Clinical validation of the existing definition is required.
Adult ; Cough* ; Epidemiologic Studies ; Epidemiology ; Female ; Humans ; Odds Ratio ; Population Characteristics ; Prevalence ; Specialization