Prevalence and causes of subacute cough in Japan

Subacute cough is subdivided and distinguished from chronic cough, because post-infectious cough is considered to be the main cause of subacute cough and differs from acute and chronic cough. However, the details of the spectrum and frequency of causes of subacute cough remain unclear because only two studies on subacute cough have been published.

Patients who presented with cough that lasted for 3-8 weeks and visited respiratory clinics or hospitals affiliated with the Japan Cough Society during 2 years were studied.

A total of 148 patients were prospectively enrolled, and those who did not meet the definition of subacute cough were excluded. Ninety-seven (68.3%) patients with subacute cough progressed to chronic cough, and the main causative diseases were cough variant asthma in 44 patients, atopic cough in 24 patients, sinobronchial syndrome in 13 patients, and post-infectious cough in seven patients. Patients with cough variant asthma complicated by atopic cough and those in whom the cause of subacute cough was unknown tended to develop chronic cough.

This study shows that post-infectious cough is less common than previously thought and the main causes of subacute cough are cough variant asthma, atopic cough, and sinobronchial syndrome and their complications. Cough variant asthma in combination with atopic cough also can be a precursor of refractory chronic cough. The careful diagnosis and treatment of two or more causative diseases is required in patients with subacute cough.