LAKE TAHOE, CALIF. – results from a large, retrospective cohort study demonstrated.
“The atopic march is characterized by a progression from atopic dermatitis, usually early in childhood, to subsequent development of allergic rhinitis and asthma, lead study author Joy Wan, MD, said at the annual meeting of the Society for Pediatric Dermatology. “It is thought that the skin acts as the site of primary sensitization through a defective epithelial barrier, which then allows for allergic sensitization to occur in the airways. It is estimated that 30%-60% of AD patients go on to develop asthma and/or allergic rhinitis. However, not all patients complete the so-called atopic march, and this variation in the risk of asthma and allergic rhinitis among AD patients is not very well understood. Better ways to risk stratify these patients are needed.”
One possible explanation for this variation in the risk of atopy in AD patients could be the timing of their dermatitis onset. “We know that atopic dermatitis begins in infancy, but it can start at any age,” said Dr. Wan, who is a fellow in the section of pediatric dermatology at the Children’s Hospital of Philadelphia. “There has been a distinction between early-onset versus late-onset AD. Some past studies have also suggested that there is an increased risk of asthma and allergic rhinitis in children who have early-onset AD before the age of 1 or 2. This suggests that perhaps the model of the atopic march varies between early- and late-onset AD. However, past studies have had several limitations. They’ve often had short durations of follow-up, they’ve only examined narrow ranges of age of onset for AD, and most of them have been designed to primarily evaluate other exposures and outcomes, rather than looking at the timing of AD onset itself.”
For the current study, Dr. Wan and her associates set out to examine the risk of seasonal allergies and asthma among children with AD with respect to the age of AD onset. They used data from the Pediatric Eczema Elective Registry (), an ongoing, prospective U.S. cohort of more than 7,700 children with physician-confirmed AD ( . All registry participants had used pimecrolimus cream in the past, but children with lymphoproliferative disease were excluded from the registry, as were those with malignancy or those who required the use of systemic immunosuppression.
The researchers evaluated 3,966 subjects in PEER with at least 3 years of follow-up. The exposure of interest was age of AD onset, and they divided patients into three broad age categories: early onset (age 2 years or younger), mid onset (3-7 years), and late onset (8-17 years). Primary outcomes were prevalent seasonal allergies and asthma at the time of registry enrollment, and incident seasonal allergies and asthma during follow-up, assessed via patient surveys every 3 years.