Capsaicin induced cough and urge-to-cough in elderly individuals with NTM (1178.6)
Mycobaterium avium complex infection is a type of nontuberculous mycobacterial (NTM) infections have been reported often occurred in elderly, white, thin and principally nonsmoking women. It has been postulated that such disease in woman is related to the way they cough. They often cough quietly and covertly, thereby the clearance of sputum is suppressed. In this study, we hypothesized that NTM subjects may have decreased cough sensitivity as measured by a higher threshold for inducing cough and the Urge-to-Cough compared to controls. Female, white and elderly NTM and control subjects were recruited in the study. Four concentrations of capsaicin (50, 100, 200, 500 uM) plus placebo (0 uM capsaicin) were presented to the subject three times each in a blinded-randomized block order. Each capsaicin presentation was separated approximately 1 min. At the end of each capsaicin presentation, subjects were asked to rate their Urge-to-Cough using the modified Borg scale from 1 (no Urge-to-Cough) to 10 (maximum Urge-to-Cough). Cough response was defined as single or multiple coughs elicited by capsaicin inhalation. There was no significant difference in cough response. NTM subjects showed lower Urge-to-Cough at the lowest capsaicin concentration compared to control subjects (p<0.05). There were no significant differences in the Urge-to-Cough score between NTM and control subjects when the capsaicin concentration was greater than 50 uM. The result suggests that NTM subjects have lower Urge-to-Cough sensitivity to low concentration capsaicin compared to control subjects. This result may explain why they have a reduced cough when the stimulus is relatively small.