House dust mite allergen reduction and allergy at 4 yr: follow up of the PIAMA-study.

Exposure to high allergen levels in early life is a risk factor for the development of allergy. We previously reported limited effects of mite allergen impermeable mattress covers in the prevention and incidence of asthma and mite allergy (PIAMA) cohort at the age of 1 and 2 yr. We now present the results of follow-up at 4 yr objectives. To examine the effects of early reduction of house dust mite (HDM) allergen exposure by means of mattress covers on the incidence of allergy and asthma symptoms in the PIAMA birth cohort at the age of 4 yr. High-risk children (allergic mother) were prenatally recruited and randomly allocated to three groups; receiving mite allergen impermeable mattress covers (n = 416), placebo covers (n = 394) or no intervention (n = 472). At 4 yr of age, atopy was assessed by questionnaire; specific Immunoglobulin E (IgE) to inhalant and food allergens was measured in serum. Dust samples collected from the children's mattresses were analysed for mite allergens. Dermatophagoides farinae1 allergen (Der f 1) levels in dust were reduced in the active group. However, Dermatophagoides pteronissinus 1 (Der p 1) levels, sensitization and atopic symptoms were similar in all groups. We found no effect of mite allergen impermeable mattress covers on sensitization and atopy at 4 yr. Moreover, the allergen reducing effects of the covers had disappeared for one of the two mite allergens that were measured.

Interrupter resistance and wheezing phenotypes at 4 years of age.

It is difficult to distinguish young children with respiratory symptoms who will develop asthma from those with transient symptoms only. Measurement of interrupter resistance may help to identify children at high risk of asthma. The aim of this study is to compare interrupter resistance in 4-year-old children with different wheezing phenotypes. All children participated in the Prevention and Incidence of Asthma and Mite Allergy cohort, a prospective birth cohort of more than 4,000 children. At 4 years of age, data on interrupter resistance plus wheezing phenotype were available for 838 children. Mean interrupter resistance values (95% confidence interval) were 0.95 (0.93, 0.97), 0.95 (0.92, 0.98), 0.96 (0.87, 1.05), and 1.08 (1.02, 1.14) kPa.L(-1).second for never (n = 482), early transient (n = 236), late-onset (n = 22), and persistent (n = 98) wheezing phenotypes, respectively. Additional analyses were performed for children with atopic and nonatopic mothers separately. Both in children with atopic and nonatopic mothers, children with persistent wheeze had significantly higher interrupter resistance values than children with never and early wheeze. In conclusion, mean interrupter resistance values were higher in children with persistent wheeze as compared with children with never and early transient wheezing phenotypes.

Fatty acids in breast milk of allergic and non-allergic mothers: The PIAMA birth cohort study.

Fatty acid composition was studied in breast milk of allergic and non-allergic mothers, focusing in particular on concentrations of the n-6 and n-3 long-chain polyunsaturates (LCP) in relation to maternal allergy. Milk samples were obtained from 168 mothers with asthma or inhalant allergies and 107 mothers without asthma and inhalant allergies, between 2 and 35 weeks after delivery. Mean values of fatty acid concentration (weight% of total fatty acids) were estimated for individual fatty acids, for groups of fatty acids and for the metabolic index (the ratio between the sum of n-6 polyunsaturates and linoleic acid). For the most relevant fatty acids, the association with maternal allergy was subsequently analyzed in more detail using multiple regression analysis. The metabolic index in breast milk was significantly lower in the allergic than in the non-allergic mothers, but no significant differences were observed in the concentrations of any of the n-6 fatty acids. Also concentrations of the n-3 fatty acids and nearly all other fatty acids were similar in allergic and non-allergic mothers' breast milk. No differences in fatty acid concentrations were observed between mothers with asthma and mothers with single or with multiple inhalant allergies. Our data suggest that differences in fatty acid composition between breast milk of allergic and non-allergic mothers are small and are unlikely to be responsible for the differential effects of breastfeeding by allergic and non-allergic mothers that have been observed in some studies.