According to data from the Centers for Disease Control and Prevention, asthma currently ranks as the second most common chronic illness in children. It has not gone unnoticed that this coincides with an increased use of antibiotics in young children. To determine whether there is a link, Canadian researchers conducted a metaanalysis of studies examining the association between the number of courses of antibiotic therapy received in infancy and the later development of asthma.
They included studies published from January 1966 to September 2004 if the studies "explicitly defined antibiotic exposure as the receipt of at least one prescription for an antibiotic in the first year of life, and included the development of physician-diagnosed childhood asthma between the ages 1 and 18 years as an outcome." The eight studies (out of more than 2,000 reviewed) that met these criteria involved a total of more than 12,000 children and 1,817 asthma cases. Four of the eight studies were prospective and four were retrospective.
Pooling the findings from all eight studies suggested an association between antibiotic treatment during the first year of life and subsequent diagnosis of asthma. When subgroup analysis was performed, however, this association was significant in the retrospective but not in the prospective studies. Methodologic limitations could account for this difference because most retrospective studies used parent-reported data rather than medical records, thus raising concerns of recall bias.
Other limitations of the studies include the relatively small sample sizes (the largest involved 4,178 patients), varying analytic approaches, and inconsistency regarding which confounders were adjusted for. Of particular concern was the presence of asthma in some children before antibiotic prescriptions were given, which could have resulted in more frequent diagnosis of upper respiratory tract infection and more frequent antibiotic use. Only one retrospective study involved high-risk children.
The investigators concluded that the findings from their metaanalysis showed a positive association between the use of antibiotics and a later diagnosis of asthma but call for "large-scale, prospective studies . . . to confirm this potential association."
Marra F et al. Chest 2006;129(3):610-8.