Cough-reflex sensitivity to inhaled capsaicin in COPD associated with increased exacerbation frequency.

Background and objective: The causes of exacerbations in COPD patients are poorly understood. This study examined the association between cough-reflex sensitivity in patients with stable COPD and the frequency of subsequent exacerbations. Methods: The sampling frame for cases and controls for this study was patients attending a hospital outpatient clinic. cough-reflex sensitivity was evaluated using the log concentration of capsaicin causing five or more coughs (log C₅). Subsequent COPD exacerbations were identified prospectively via symptom-based diaries over a 12-month period. Results: The study group comprised 45 COPD subjects and 10 controls. Mean log C₅ was lower in the COPD group than in the control group (0.97 (95% confidence interval (CI): 0.76–1.18) versus 1.26 (95% CI: 0.81–1.71), P = 0.095). In the COPD group, log C₅ was negatively correlated with serum CRP level ( r = −0.36, P = 0.02) and significantly associated with the exacerbation frequency ( r = −0.38, P = 0.01). Stepwise multiple regression analysis showed that cough-reflex sensitivity was significantly associated with exacerbation frequency ( r² = 0.15, P = 0.01). Conclusions: Hypersensitivity of the cough reflex to inhaled capsaicin might reflect airway inflammation in stable COPD patients, which predisposes to frequent exacerbations. [ABSTRACT FROM AUTHOR]