Importance of atopic cough, cough variant asthma and sinobronchial syndrome as causes of chronic cough in the Hokuriku area of Japan

Objective: A prospective multicentre study was conducted to elucidate the causes of chronic cough in Japan. Methodology: All consecutive and unselected patients complaining of cough lasting 8 weeks or more, who visited our clinics from 1 June to 31 December 2001, were registered. The causes of chronic cough were diagnosed based on the criteria for definite and probable causes of cough as recommended by the Japanese Cough Research Society. Results: Of the 248 patients enrolled, 72 patients (29.0%) were unavailable for follow up before their diagnostic assessment had been finalized. Among the 176 patients who were adequately assessed, a diagnosis was made in 165 patients (93.7%) either as single cause or as one of two casuses: atopic cough in 48 (29.1%) and 11 patients (6.7%); cough variant asthma in 46 (27.9%) and nine patients (5.5%); cough predominant asthma in 14 (8.5%) and three patients (1.8%); and sinobronchial syndrome (SBS) in 28 (17.7%) and 14 patients (8.5%), respectively. A diagnosis of gastro-oesophageal reflux-associated cough was made in a total of four patients (2.4%). Conclusion: Atopic cough, asthmatic cough consisting of cough variant asthma and cough predominant asthma, and SBS are major causes of chronic cough in Japan.