Multifaceted allergen avoidance during infancy reduces asthma during childhood with the effect persisting until age 18 years.

BACKGROUND: Asthma is a chronic disease that often starts in childhood. The key risk factors are a child's environment and their genetic characteristics. The aim of this study was to evaluate the efficacy of environmental modification in the first 12 months of life on the prevalence of asthma in high-risk individuals. METHODS: Children (n=120) considered at high risk of allergic disorders (either dual heredity or single heredity and a high cord total IgE), were enrolled in a single-blinded, randomised controlled trial. Infants in the intervention arm were either breast fed with the mother on a low allergen diet or given an extensively hydrolysed formula. Exposure to house dust mite allergen was reduced. The control group followed standard advice. Children were assessed at ages 1, 2, 4, 8 and 18 years for the presence of asthma and atopy. RESULTS: At 18 years of age, there was a significantly lower prevalence of asthma in the prevention group compared with the control group (OR: 0.23, 95% CI 0.08 to 0.70, p=0.01), primarily due to asthma that developed during childhood but persisted until age 18 years. Repeated-measure analysis showed that there was an overall reduction in asthma prevalence from 1 to 18 years (OR: 0.51, CI 0.32 to 0.81, p=0.04). Prevalence of atopy was not significantly different between the two groups at age 18. CONCLUSION: Comprehensive allergen avoidance in the first year of life is effective in preventing asthma onset in individuals considered at high risk due to heredity. The effect occurs in the early years, but persists through to adulthood.

Characterisation of asthma that develops during adolescence; findings from the Isle of Wight Birth Cohort.

BACKGROUND: Understanding of adolescent-onset asthma remains limited. We sought to characterise this state and identify associated factors within a longitudinal birth cohort study. METHODS: The Isle of Wight Whole Population Birth Cohort was recruited in 1989 (N=1456) and characterised at 1, 2, 4, 10 and 18-years. "Adolescent-onset asthma" was defined as asthma at age 18 without prior history of asthma, "persistent-adolescent asthma" as asthma at both 10 and 18 and "never-asthma" as those without asthma at any assessment. RESULTS: Adolescent-onset asthma accounted for 28.3% of asthma at 18-years and was of similar severity to persistent-adolescent asthma. Adolescent-onset asthmatics showed elevated bronchial hyper-responsiveness (BHR) and atopy at 10 and 18 years. BHR in this group at 10 was intermediate to that of never-asthmatics and persistent-adolescent asthma. By 18 their BHR, bronchodilator reversibility and sputum eosinophilia was greater than never-asthmatics and comparable to persistent-adolescent asthma. At 10, males who later developed adolescent-onset asthma had reduced FEV(1) and FEF(25-75), while females had normal lung function but then developed impaired FEV(1) and FEF(25-75) in parallel with adolescent asthma. Factors independently associated with adolescent-onset asthma included atopy at 10 (OR=2.35; 95% CI=1.08-5.09), BHR at 10 (3.42; 1.55-7.59), rhinitis at 10 (2.35; 1.11-5.01) and paracetamol use at 18-years (1.10; 1.01-1.19). CONCLUSIONS: Adolescent-onset asthma is associated with significant morbidity. Predisposing factors are atopy, rhinitis and BHR at age 10 while adolescent paracetamol use is also associated with this state. Awareness of potentially modifiable influences may offer avenues for mitigating this disease state.

Adjusting wheal size measures to correct atopy misclassification.

PURPOSE: Skin prick testing (SPT) is fundamental to the practice of clinical allergy identifying relevant allergens and predicting the clinical expression of disease. Wheal sizes on SPT are used to identify atopic cases, and the cut-off value for a positive test is commonly set at 3 mm. However, the measured wheal sizes do not solely reflect the magnitude of skin reaction to allergens, but also skin reactivity (reflected in the size of histamine reaction) and other random or non-random factors. We sought to estimate wheal sizes exclusively due to skin response to allergens and propose gender-specific cutoff points of atopy. METHODS: We developed a Bayesian method to adjust observed wheal sizes by excluding histamine and other factor effects, based on which revised cutoff points are proposed for males and females, respectively. The method is then applied to and intensively evaluated using a study population aged 18, at a location on the Isle of Wight in the United Kingdom. To evaluate the proposed approach, two sample t-tests for population means and proportion tests are applied. RESULTS: Four common aeroallergens, house dust mite (HDM), grass pollen, dog dander, and alternaria are considered in the study. Based on 3 mm cutoff, males tend to be more atopic than females (P-values are between 0.00087 and 0.062). After applying the proposed methods to adjust wheal sizes, our findings suggest that misclassifications of atopy occur more often in males. Revised allergen-specific cutoff values are proposed for each gender. CONCLUSION: To reduce the gender discrepancy, we may have two potentially convenient solutions. One way is to apply allergen-specific and gender-specific cutoff values following the proposed method. Alternatively, we can revise the concentration of allergens in the SPT solutions but keep the cutoff values unchanged, which may be more convenient to clinicians.

Influence of atopy and asthma on exhaled nitric oxide in an unselected birth cohort study.

BACKGROUND: Asthma is considered to be associated with elevated levels of exhaled nitric oxide (FeNO). The nature of this relationship and how it is influenced by atopy are still not resolved. METHODS: The Isle of Wight birth cohort (N=1456) was reassessed at 18 years of age. Participants able to attend the research centre were assessed by questionnaires, skin prick testing and FeNO in order to explore the interrelationship between asthma, atopy and FeNO. RESULTS: Atopy was significantly associated with higher levels of FeNO. However, the level of FeNO for non-atopic asthmatic participants was no different to the non-atopic no-asthma group. The highest levels of FeNO were seen in subjects with both atopy and asthma. In addition, FeNO was positively associated with increasing atopic burden as evidenced by increasing FeNO with increasing skin prick testing positivity, and with increasing severity of atopic asthma as evidenced by the number of attacks of wheezing. FeNO and current inhaled corticosteroid use were not significantly associated. CONCLUSIONS: FeNO behaves as a biomarker of atopy and the "allergic asthma" phenotype rather than asthma itself. This may explain why FeNO-guided asthma treatment outcomes have proved to be of limited success where atopic status has not been considered and accounted for.

A comparison of the effects on Canadian boreal forest lichens of nitric and sulphuric acids as sources of rain acidity.

The effects of different levels of nitrate and sulphate in acidic precipitation on the growth of the lichens Cladina rangiferina (L.) Wigg. and C. stellaris (Opiz.) Brodo were compared. Permanent Held plots in a Canadian boreal forest ecosystem received two years of spraying with artificial rains of pH 4.2 (ambient), 3.5 or 2.8, each containing one of four molar ratios of sulphate to nitrate, i.e. sulphuric acid alone, nitric acid alone: 2:1 or 1:2. A substantial fertilization effect was observed when C. rangiferina was watered with rain of pH 2.8, derived from nitric acid alone. Compared with before-treatment values, gains in mean dry weight (+ 62%) and mean podetial height (+14%) were obtained for this species, in addition to elevated levels of N in air-dried tissues. Post-treatment values for the mean dry weight of C. rangiferina were significantly reduced for those podetia sprayed with rain of low pH, derived from sulphuric acid alone. Although podetia of C. stellaris were stimulated by rains of pH 4.2, based on a higher concentration of nitric acid, there was no N fertilization following the most acidic sprays. Data from this study support the view that the N content of acidic rain can cause a short-term growth stimulation for those species able to absorb nitrate from solution. However, beneficial effects on growth of prolonged fertilization via acid rain inputs are unlikely.

THE EFFECT OF WINTER FIELD CONDITIONS ON THE DISTRIBUTION OF TWO SPECIES OF UMBILICARIA: I. CO2 EXCHANGE IN RECIPROCALLY-TRANSPLANTED THALLI.

Two lichen species of the genus Umbilicaria were transplanted into each other's habitat in order to determine the role of winter field conditions in regulating distribution patterns. U. vellea (L.) Ach., which normally grows in a steeply inclined, snow free habitat, was transplated into the level-ground, snow-covered habitat of U. deusta (L.) Baum. The opposite was done for U. deusta. Suitable controls to test the effect of transplanting were also run for both species. The reciprocal transplantation was done in each of two years, one of which had a normal snow load, the other which had almost no snow cover. The effect of reciprocal transplantation was to reduce significantly the carbon fixing ability in U. vellea in the year with the normal snow-load. Transplantation had no effect on U. deusta. The effects on CO2 exchange were only slight for U. vellea in the year with the lesser snow-load. It is therefore concluded that existing winter field conditions, and especially the nature of the snow cover, maintain the existing distribution pattern of the lichens in the field.