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Causes and outcome in cough

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1H. Sumner, 1A. Kelsall, 2A. L. Lazaar, 1U. Kolsum, 1D. Singh, 1A. A. Woodcock, 1J. A. Smith. 1Respiratory Research Group, University of Manchester, Manchester, UK, 2Respiratory CEDD Discovery Medicine, GlaxoSmithKline, USA

Introduction Patients with chronic obstructive pulmonary disease (COPD) complain of cough and mucus hypersecretion. The mechanisms underlying cough are likely to be multifactorial and are poorly understood. We aimed to investigate the effect of smoking on objective cough frequency in both patients with COPD and healthy volunteers.

Methods We studied 68 patients with COPD from the ECLIPSE cohort (median age 66 years (interquartile range (IQR) 61–71), median forced expiratory volume in 1 s (FEV1) 59.5% predicted (IQR 44.3–75.3), 22 female, 23 current smokers), 12 healthy smokers (median age 60 years (IQR 57–60), median FEV1 91.6% predicted (IQR 43.7–71.0), 7 female) and 12 healthy non-smokers (median age 58 years (IQR 43–68), median FEV1 117.0% predicted (IQR 103.0–122.8), 8 female). All subjects underwent 24 h objective cough monitoring (Vitalojak, Vitalograph), spirometry and capsaicin cough reflex sensitivity testing.

Results Significant differences in 24 h cough rates were seen between subject groups (p<0.001). COPD current smokers had the highest cough rates (median 9.0 coughs/h (IQR 4.3–15.6)); COPD ex-smokers and healthy smokers had similar cough rates (median 4.9 coughs/h (IQR2.3–8.7) and 5.3 cough/h (IQR 1.2–8.3), p = 0.60) which were about half those of COPD current smokers (p = 0.018 and p = 0.03). Healthy volunteer cough rates (median 0.7 coughs/h (IQR 0.2–1.4)) were lowest. Objective cough rates were not influenced by age or gender. Cough reflex sensitivity was not significantly different between groups (logC5 p = 0.35, logC2 p = 0.36) but was weakly correlated with cough frequency (logC5 r = −0.36, p = 0.004 and logC2 r = −0.31, p = 0.001). …

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