Cough-reflex sensitivity to inhaled capsaicin in COPD associated with increased exacerbation frequency.
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 C(5)). 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 C(5) 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 C(5) 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 (r(2) = 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.
Terada
Kunihiko
K
Department of Respiratory Medicine, Kyoto University, Kyoto 606-8507, Japan.
Muro
Shigeo
S
Ohara
Tadashi
T
Haruna
Akane
A
Marumo
Satoshi
S
Kudo
Megumi
M
Ogawa
Emiko
E
Hoshino
Yuma
Y
Hirai
Toyohiro
T
Niimi
Akio
A
Mishima
Michiaki
M
D000368:Aged; D002097:C-Reactive Protein / Q000378:metabolism; D002211:Capsaicin / Q000009:adverse effects*; D015984:Causality; D003371:Cough / Q000453:epidemiology / Q000503:physiopathology*; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012018:Reflex / Q000502:physiology*; D012044:Regression Analysis; D012130:Respiratory Hypersensitivity / Q000097:blood / Q000139:chemically induced* / Q000503:physiopathology*; D018689:Sensory System Agents / Q000009:adverse effects; D012720:Severity of Illness Index; D014797:Vital Capacity / Q000502:physiology
D018689:Sensory System Agents; D002097:C-Reactive Protein; D002211:Capsaicin