Children with asthma whose fathers have a history of the disease are at significantly greater risk for serious airway constriction than children whose father have no such history.

In reporting the results of a 5-year study, the investigators said that paternal asthma was strongly associated with childhood airway hyperresponsiveness (AHR), an exaggerated constricting response to various stimuli that characterize asthma.

Called a defining feature of asthma, AHR is directly correlated with pulmonary symptoms and disease severity, according to the authors.

The 1,041 children in the study were all participants in the Childhood Asthma Management Program (CAMP). Sponsored by the National Institutes of Health and the Canadian Institutes of Health Research, CAMP is the largest outcome study of mild to moderate asthma in children to be undertaken. The multicenter investigation, which enrolled children ages 5 to 12, was designed to determine the long-term effects of three inhaled treatments.

While other studies have demonstrated that parental history of asthma affects children, the authors of the latest study note that they are the "first to suggest that a parental history of asthma influences the natural history of airway responsiveness among children with established asthma, and that the father's history may be the predominant familial determinant of this relationship."

AHR was measured through a median logarithmic data analysis of PC20, the concentration of the bronchoconstrictor methacholine required to cause a 20 percent fall in the children's lung function test scores. (All participants took the methacholine test at the beginning of the study and yearly thereafter.)

Lower data analysis scores showed worse AHR: the results ranged from 0.84 in the 208 children who had a father with asthma to 1.13 in the 763 youngsters who did not. The correlation was even greater when both parents had asthma: 0.52 in children with two asthmatic parents and 1.17 in children without parental asthma. The researchers did not find a statistically significant correlation between maternal asthma and childhood AHR.