EARLY SENSITIZATION TO HOUSE DUST MITE IS A MAJOR RISK FACTOR FOR SUBSEQUENT DEVELOPMENT OF BRONCHIAL ASTHMA IN JAPANESE INFANTS WITH ATOPIC DERMATITIS: RESULTS OF A 4-YEAR FOLLOW-UP STUDY
Ohshima Y, Yamada A, Hiraoka M, et al. Ann Allergy Asthma Immunol. 2002;89:265–270
Purpose of the Study.
To clarify factors involved in the development of bronchial asthma (BA) in children with atopic dermatitis (AD).
One hundred sixty-nine infants (age <12 months) with AD who had been seen in the pediatric outpatient clinics of Kyoto, Gunma, and Gifu University Hospitals and affiliated hospitals between August 1994 and July 1995. The infants had neither BA nor episodes of recurrent wheezing at time of registration.
Patients were followed for 4 years. The outcome of AD, development of BA, and changes in immunologic and other parameters were examined. Total immunoglobulin (IgE) levels and specific IgE against house dust mite (HDM), egg white, cow’s milk, wheat, rice, and soybean were examined using the CAP-RAST (radioallergosorbent test). Family history of AD and BA among relatives was obtained from interviews with the parents. Risk factors for the development of BA were analyzed for each follow-up year.
One hundred three children remained in the study at the 4-year follow-up. Thirty-five percent had been diagnosed with asthma by pediatric allergists and 10.7% had episodes of wheezing, but were not diagnosed with asthma. Eighty-five percent of patients had specific IgE levels against at least 1 of the following 5 food allergens (egg white, milk, wheat, soybean, and rice). HDM-specific IgE increased from 11% at registration to 59% at the 1-year follow-up and 87% at the 4-year follow-up. Patients who developed BA showed early appearance of HDM-specific IgE and persistently high levels of food-specific IgE. Male sex, a positive family history of BA, and the appearance of HDM-specific IgE were identified as significant risk factors for the early development of BA, but the significance of these parameters decreased afterward. A positive family history of AD, the outcome of AD, and the keeping of furred pets were also identified as risk factors during part of the follow-up years. During the 4-year follow-up period, AD cleared in 33.8%, improved in 51.4%, was unchanged in 11.7% and worsened in 2.9% of the patients.
The early appearance of HDM-specific IgE antibodies in early childhood is a major risk factor for the subsequent development of BA in children with AD. However, the influence decreases after longer follow-up.
This study supports the idea that early atopic sensitization to food is a risk factor for subsequent inhalant sensitization and, therefore, a risk factor for the development of asthma. Risk factors appeared to shift during the 4-year follow-up, but this may have been influenced by the loss of 39% if the original study population. Furred animals also appeared to be a risk factor in the development of asthma, contrary to some recent studies claiming that a pet in the home might have some protective effect. Unfortunately, the authors did not obtain animal-specific IgE levels. Studies in infants with AD where occlusive bedding is used as an intervention to reduce HDM sensitization and possibly, by extension, asthma, would prove interesting.