Cough frequency, cough sensitivity and health status in patients with chronic cough.

BACKGROUND Little is known about the frequency of cough in health and in patients with chronic cough. METHODS We measured cough frequency and its relationship with other markers of cough severity in 20 patients with chronic cough and 9 healthy subjects using the Leicester Cough Monitor (LCM), which is an automated ambulatory digital cough monitor that records sound only. All subjects had a 6-h recording and recordings were manually counted. A subgroup of 6 normals and 6 patients with a stable chronic cough had repeat measurements up to 6 months apart. RESULTS Mean (sem) cough counts/hour were 43(8) in patients with chronic cough and 2(1) in normals (mean difference 41; 95% confidence interval 24-59; P<0.001). The cough counts were repeatable (within subject standard deviation: 23 coughs/hour; intraclass correlation coefficient 0.8). Cough counts correlated significantly with physical (r=-0.6, P=0.03), social (r=-0.7, P=0.01) and total Leicester Cough Questionnaire (LCQ) health status scores (r=-0.6, P=0.03) and cough sensitivity (concentration of capsaicin causing 5 coughs: r=0.9, P=0.008). CONCLUSION We have shown that there are marked differences in cough frequency between patients with chronic cough and healthy subjects, that these measurements are repeatable, and that they correlate with cough-specific health status.