Impaired cough sensitivity in children of smokers.

INTRODUCTION: Exposure to environmental tobacco smoke puts children at greater risk for respiratory tract infection and other illnesses and increases the risk that children later become habitual smokers. Because cough sensitivity may relate to both illness and smoking initiation, we determined whether this vital reflex is impaired in children living with smokers. METHODS A single-inhalation capsaicin challenge was administered to 2 groups of healthy children (16 females, 22 males; 10-17 years old) and parents (25 mothers, 1 father): exposed children (n = 17) and parents (n = 13) who smoked ~10 cigarettes/day; and age-matched children (n = 21) never exposed to smoke at home and parents who never smoked in their lifetimes (n = 13). The lowest capsaicin concentrations that triggered (a) sensations of tingle, sting, or burn (irritation threshold) and (b) at least two coughs (cough threshold) were determined. RESULTS Cough thresholds were 2 times as high in exposed children (15.00 µM; 95% confidence interval (CI): 9.98-22.55 µM) as in non-ETS-exposed children (7.31 µM; CI: 5.25-10.19 µM, p = .003). Smoking parents also had higher cough thresholds than never-smoker parents (p = .009). Throat irritation was reported at concentrations below cough threshold for both children and parents. Irritation thresholds did not differ significantly between the two groups of children but were higher for smoking parents than for never-smokers (p = .027). CONCLUSIONS We provide the first evidence that the cough reflex is impaired in seemingly healthy children who live with smokers. The 2-fold difference in cough threshold is comparable in magnitude to the change that occurs with acute respiratory tract infection.