Prevalence of Suspected Obstructive Sleep Apnea Among Patients With Chronic Cough and Relatively Low BMI

Background/Aim: Recent studies have suggested an association between chronic cough and obstructive sleep apnea (OSA). This study aimed to estimate the prevalence of suspected OSA and describe associated clinical characteristics among Japanese adults with chronic cough. Patients and Methods: Outpatients with chronic cough were recruited from three Japanese institutions between March 2023 and February 2025. Eligible participants were ≥20 years old with a cough lasting >8 weeks. Overnight home sleep apnea testing was performed to assess the respiratory event index (REI), and suspected OSA was defined as an REI ≥5 events/h. Cough-related symptoms were assessed using the visual analog scale (VAS) and the Japanese version of the Leicester Cough Questionnaire (J-LCQ), and daytime sleepiness was evaluated using the Epworth Sleepiness Scale (ESS). REI was compared across causes of chronic cough. Patients were stratified by REI ≥15 events/h. Correlations between the REI and age, body mass index (BMI), VAS score, and J-LCQ score were evaluated. Results: This study enrolled 23 patients (median age, 56.0 years; 11 men). The median BMI was 25.2 kg/m2. Suspected OSA was present in 20 patients (87.0%), despite a median ESS score of 7.0. The median REI was 15.6 events/h and was elevated regardless of the cause of chronic cough. REI ≥ 15 events/h was associated with older age (p=0.04), whereas BMI did not differ significantly between the groups. J-LCQ scores were not significantly associated with the REI. Conclusion: REI was high in patients with chronic cough, suggesting a high prevalence of suspected OSA despite their relatively low BMI. These findings suggest obesity-independent mechanisms and support OSA screening even in patients without daytime sleepiness.