Relationship between bronchial hyperresponsiveness and development of asthma in children with chronic cough

To evaluate the relationship between bronchial hyperresponsiveness (BHR) an d the development of asthma in children with chronic cough, we performed me thacholine inhalation challenges and transcutaneous oxygen pressure (tcPO(2 )) measurements in 92 children with chronic cough aged from 1-13 years (55 boys and 37 girls; mean, 5.3 years) and followed them for greater than or e qual to 10 years. Forty-four age-matched children with asthma (24 males and 20 females; mean, 6.5 years) and 44 age-matched children without cough or asthma served as controls (18 males and 26 females; mean, 4.6 years). Conse cutive doubling doses of methacholine were inhaled until a 10% decrease in tcPO(2) from baseline was observed. The cumulative dose of methacholine at the inflection point of the tcPO(2) record (Dmin-PO2) was considered to rep resent hyperresponsiveness to inhaled methacholine. After 10 years or more of follow-up, 60 of the 92 subjects with cough answe red our questionnaire, and 27/60 had been diagnosed with asthma. There was a statistical difference in Dmin-PO2 between the children who presented wit h chronic cough originally and who developed asthma (asthma-developed group ) and those who did not develop asthma (asthma-free group). There was no di fference in the value of Dmin-PO2 between the asthma-developed group and th e asthma group, or between the asthma-free group and the age-matched contro l group. Among the children with chronic cough, there was no difference in Dmin-PO2 between girls and boys, either in the asthma-developed group or in the asthma-group. We conclude that 45% of the children with a chronic cough in early life dev eloped asthma, and that BHR in children with chronic cough during the child hood period is a strong risk factor for the development of asthma. (C) 2001 Wiley-Liss, Inc.