Background: Upper airway cough syndrome (UACS) is generally considered a common cause of chronic cough but remains poorly recognised in Japan. Objective: This study aimed to assess whether UACS was a common cause of chronic cough in Japan, as is true in other countries. Interview and examination items were evaluated for their potential use in UACS diagnosis. Methods: All patients with chronic cough were preliminarily diagnosed with bronchial asthma, UACS, gastroesophageal reflux disease, or postinfectious prolonged cough, based on interviews and examinations. Treatment centred on nasal steroids was administered to the UACS group and standard treatment to the other groups. The observation period lasted 4 weeks. The subjective cough score at first diagnosis was set at 10, and the final diagnosis was made based on the treatment administered at the time the cough score had decreased to <= 2.The associations between the presence or absence of UACS and interview and examination items were statistically evaluated. Results: Among 230 patients with chronic cough, 146 were diagnosed with UACS-only. Multivariate logistic regression revealed that the assessment items 'awareness of mucus accumulating in the back of the throat', 'presence of abnormal echography findings', 'absence of associated coughing when exercising' and 'presence of coughing persisting after onset' were significantly correlated with the presence or absence of UACS (p < 0.05). Conclusions: UACS may be the most common cause of chronic cough in Japan and may be effectively treated with nasal corticosteroids. Diagnosing UACS might be possible by selecting appropriate interview and examination items. Lay summary Chronic cough that lasts more than 8 weeks is often a symptom that plagues the patient and the physician. In general, postnasal drip [now defined as upper airway cough syndrome (UACS)] associated with rhinosinusitis, cough variant asthma and gastroesophageal reflux are known causes of chronic cough. The cough guidelines by the Japanese Respiratory Society state sinusitis as the cause of cough, and it is categorised as a sino-bronchial syndrome. Thus, the recognition of UACS is extremely low. UACS is not considered a cause of cough in Japan, but it is unlikely that Japan is the only exception. Based on these findings, I investigated the causes of chronic cough in patients who visited my clinic. As a result, UACS accounted for at least 60% of chronic cough cases. This study showed that UACS might be the most common cause of chronic cough in Japan. This study also showed that the treatment centred on nasal steroids was highly effective against UACS and that some interview and examination items might be useful in the diagnosis of UACS. This is an unprecedented finding and may contribute to the diagnosis of chronic cough.
