Clinical significance of airway responsiveness in children of low birthweight.

We report a prospective study of airway responsiveness in a cohort of 121 children of low birthweight (under 2,000 g) at 7 years and a random sample of 100 local schoolchildren of the same age. A positive airway response was defined as a 20% fall in peak expiratory flow rate in response to a cumulative histamine dose of 3 mumol or less. We found a moderate increase in airway responsiveness to inhaled histamine in the cohort (44%) compared with the reference group (22%). There was no significant association between airway responsiveness and any perinatal variables including the level of respiratory support. The findings suggested that neonatal respiratory illness or its treatment did not play a major role in determining the long-term airway responsiveness in these children. Amongst all factors examined, reduced airway function at the age of 7 was most strongly associated with airway responsiveness, independent of perinatal and familial factors. Airway responsiveness was associated with significantly more chest symptoms. We suggest that increased airway responsiveness to inhaled histamine in low birthweight children is a consequence rather than the cause of reduced airway function and argue against the presence of any other form of airway dysfunction as a cause of airway responsiveness.