Father with Asthma Is Key to Child's Airway Constriction
Children with asthma whose fathers have a history of the disease are at significantly greater risk for serious airway constriction than children whose fathers have no such history, according to an article published in the first issue of the September 2005 American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
Reporting the results of a five-year study, Benjamin A. Raby, M.D., M.P.H., along with five associates from the Channing Laboratory at Brigham and Women's Hospital in Boston, said that paternal asthma was strongly associated with childhood airway hyperresponsiveness (AHR), an exaggerated constricting response to various stimuli that characterizes asthma.
"Among individuals with asthma, AHR is directly correlated with pulmonary symptoms and disease severity," said Dr. Raby. "It is also an important determinant of long-term outcome, not only with respect to asthma symptoms, but also to airway growth and maturation, as well as lung function decline."
The 1,041 children included in the study participated in the Childhood Asthma Management Program (CAMP). Sponsored by the U.S. 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 multi-center study, 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 this 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 the father's asthma history may be the predominant familial determinate of this relationship."
Researchers measured AHR 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 more severe AHR: results ranged from 0.84 in the 208 children whose fathers suffered from asthma to 1.13 in 763 youngsters whose fathers 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 any parental asthma. The researchers did not find a statistically significant correlation between maternal asthma and childhood AHR.
The authors said that this last finding "may seem contradictory," since other studies have found a correlation between maternal and childhood asthma. Reviewing those studies, the investigators noted that the children in those studies tended to be younger and exhibited other symptoms of asthma, like wheeze. The researchers pointed out that their study is part of a growing body of "evidence that the paternal influence increases with age."
To participate in the CAMP study, children were required to have one or more of the following characteristics: asthma symptoms at least twice per week, inhaled bronchodilator use at least twice a week or daily use of asthma medication.
Questionnaire data, including details of family medical history, were collected during an interview with the child's parents or guardian. Then, the children were assigned to one of three treatment arms, which included groups taking the anti-inflammatory medications budesonide and nedocromil sodium and groups taking a placebo compound. Spirometry was performed twice a year during follow-up sessions to measure the amount of air entering and leaving the lungs.
The researchers noted that the paternal-child correlation with AHR was independent of known determinants of airway responsiveness, including exposure to cigarette smoke, socioeconomic status and demographic factors.