Purpose of the Study
To investigate the association between Der p 1 allergen in bedding and lung function in children with wheezing.
Thirty children with history of wheezing, age 8 to 12 years, followed for 12 months in Sydney, Australia.
The levels of house dust mite (HDM) were measured at the beginning of the study in March 1994, and at 6, 8, 10, and 12 months into the study. Fifteen children with the lowest (mean, 5.5 μg/g) and 15 children with the highest (mean, 148.8 μg/g) Der p 1 levels in their bedding were included in the study. The children were skin-tested for HDM and underwent bronchial histamine challenge. The children kept an asthma diary twice a day, after waking up in the morning and in the evening before going to bed. The asthma diary included information about peak expiratory flow rate (PEFR), asthma symptoms, and medications used.
There were 16 boys and 14 girls with a mean age of 9.6 years. Seventeen children (57%) had a positive skin test to HDM, 15 children (50%) had airway hyperreactivity on histamine challenge, and 25 children (83%) had received a diagnosis of asthma from a doctor. There was no difference in the minimum PEFR between the 2 groups at baseline. Minimum PEFR improved over the study period in both groups. At baseline, compared with children without HDM sensitivity, children with HDM sensitivity had a greater proportion of days with morning wheeze, use of salbutamol in the morning, and use of inhaled steroids.Der p 1 concentrations were lowest in December but not significantly different from other times. For children with HDM atopy there was a moderate negative correlation between the log Der p 1 level and the minimum PEFR on each of the 5 occasions (correlation coefficient range: −0.35–−0.61). The correlation coefficients were statistically significant except for March and December. The association between PEFR and the log Der p 1concentration was significant (β-coefficient = −14.17,P = .024) in children with HDM atopy but not in children without HDM atopy.
This study supports the hypothesis that HDM allergens have an adverse effect on the lung function of children with wheezing.
This study has demonstrated that natural changes in HDM levels can lead to reductions in PEFR in children who are allergic to HDM. These findings highlight the importance of maintaining low HDM levels throughout the year in the home environment of children sensitized to HDM. Unfortunately, this study did not analyze other potential confounders such as animal allergens, pollens, molds, viral infections, and air pollution.