Is primary prevention of asthma possible?

Association of diabetes-related autoantibodies with the incidence of asthma, eczema and allergic rhinitis in the TRIGR randomised clinical trial

AIMS/HYPOTHESIS

This paper presents the relationship between islet autoantibodies, precursors of type 1 diabetes, and the development of persistent asthma, allergic rhinitis and atopic eczema.

METHODS

A total of 2159 newborns who had a first-degree relative with type 1 diabetes and selected HLA genotypes were followed until the youngest participant reached 10 years of age. Islet cell antibodies (ICA) were detected using indirect immunofluorescence. Autoantibodies to insulin (IAA), GAD (GADA), the tyrosine phosphatase-related insulinoma-associated 2 molecule (IA-2A) and zinc transporter 8 (ZnT8A) were quantified with the use of specific radiobinding assays. As an ancillary study, the incidence of asthma, allergic rhinitis and eczema was assessed in 1106 of these children using the International Study of Asthma and Allergies in Childhood (ISAAC) core questionnaire when the children were 9-11 years old. HRs with 95% CIs were calculated to depict the incidence of these diseases following seroconversion to autoantibody positivity.

RESULTS

The cumulative incidence of atopic eczema, allergic rhinitis and persistent asthma were 22%, 9% and 7.5%, respectively, by 9-11 years of age. The occurrence of diabetes-related autoantibodies showed a protective association with subsequently reported incidence of asthma and eczema. The incidence of rhinitis was not significantly related to the occurrence of IAA or GADA (statistical power was limited), but demonstrated the same inverse relationship as did the other diseases with ICA or when multiple autoantibodies first appeared together.

CONCLUSIONS/INTERPRETATION

The findings add evidence to the relationships between these atopic diseases and diabetes-related autoimmunity and also suggest that, for eczema, the interaction depends upon which autoantibody appeared first.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00179777 Graphical abstract.

Environmental exposure assessment in European birth cohorts: results from the ENRIECO project

Environmental exposures during pregnancy and early life may have adverse health effects. Single birth cohort studies often lack statistical power to tease out such effects reliably. To improve the use of existing data and to facilitate collaboration among these studies, an inventory of the environmental exposure and health data in these studies was made as part of the ENRIECO (Environmental Health Risks in European Birth Cohorts) project. The focus with regard to exposure was on outdoor air pollution, water contamination, allergens and biological organisms, metals, pesticides, smoking and second hand tobacco smoke (SHS), persistent organic pollutants (POPs), noise, radiation, and occupational exposures. The review lists methods and data on environmental exposures in 37 European birth cohort studies. Most data is currently available for smoking and SHS (N=37 cohorts), occupational exposures (N=33), outdoor air pollution, and allergens and microbial agents (N=27). Exposure modeling is increasingly used for long-term air pollution exposure assessment; biomonitoring is used for assessment of exposure to metals, POPs and other chemicals; and environmental monitoring for house dust mite exposure assessment. Collaborative analyses with data from several birth cohorts have already been performed successfully for outdoor air pollution, water contamination, allergens, biological contaminants, molds, POPs and SHS. Key success factors for collaborative analyses are common definitions of main exposure and health variables. Our review emphasizes that such common definitions need ideally be arrived at in the study design phase. However, careful comparison of methods used in existing studies also offers excellent opportunities for collaborative analyses. Investigators can use this review to evaluate the potential for future collaborative analyses with respect to data availability and methods used in the different cohorts and to identify potential partners for a specific research question.

The role of the intestinal microbiota in the development of atopic disorders

The prevalence of atopic diseases, including eczema, allergic rhinoconjunctivitis and asthma, has increased worldwide, predominantly in westernized countries. Recent epidemiological studies and experimental research suggest that microbial stimulation of the immune system influences the development of tolerance to innocuous allergens. The gastrointestinal microbiota composition may be of particular interest, as it provides an early and major source of immune stimulation and seems to be a prerequisite for the development of oral tolerance. In this review the observational studies of the association between the gut microbiota and atopic diseases are discussed. Although most studies indicated an association between the gut microbiota composition and atopic sensitization or symptoms, no specific harmful or protective microbes can be identified yet. Some important methodological issues that have to be considered are the microbiological methods used (traditional culture vs molecular techniques), the timing of examining the gut microbiota, the definition of atopic outcomes, confounding and reverse causation. In conclusion, the microbiota hypothesis in atopic diseases is promising and deserves further attention. To gain more insight into the role of the gut microbiota in the etiology of atopy, large-scale prospective birth cohort studies using molecular methods to study the gut microbiota are needed.

What is the role of the prevention of allergy in the first period of life?

The widespread increase in the prevalence of allergic disease, which has occurred over the last 20 y, has created general concern in Europe and in the rest of the world. The reason for this increase is still partially unknown. In this period, despite a greater understanding of the pathogenesis and risk factors of allergies plus the greater efficacy of drugs to control the symptoms, the cost of intervention and the socio-economic impact are still very high. For these reasons, prevention in the first period of life represents a goal for both developed and developing countries in order to reduce this upward trend.

Primary prevention of asthma

There has been a dramatic increase in the prevalence of asthma over the last quarter century, particularly in the industrialized world. Although our understanding of asthma continues to improve, there is no cure for the disease. Primary prevention of asthma is the focus of this review. Asthma is a disease with multiple gene-environment interactions. Candidate genes for asthma are considered, and potential interaction between one of those genes, CD14, and an environmental factor, endotoxin, is reviewed as it relates to the hygiene hypothesis. Environmental risk factors for asthma including allergens, pollutants, infectious factors, and dietary modifications are considered, particularly their potential for primary prevention of asthma. Ongoing cohort studies including the Canadian Allergy and Asthma Prevention Study, the Manchester Allergy and Asthma Study, the Children's Asthma Prevention Study from Australia, and the Prevention and Incidence of Asthma and Mite Allergy Study from the Netherlands are briefly reviewed. A more definitive understanding of genetic background and environmental triggers and their interactions is required before any specific approach to the primary prevention of asthma can be championed aggressively.

Childhood risk factors for atopy and the importance of early intervention

The increasing prevalence of atopic diseases, particularly atopy-associated asthma, has become a major challenge for allergists and public health authorities in many countries. The understanding of the natural history of the atopic march, including the determinants that are modifiable and might become candidates for preventive intervention, is still very limited. Information provided by cross-sectional studies can only generate hypotheses, which need to be supported by prospective, longitudinal, cohort studies. Ultimately, it will depend on the results of well-controlled intervention studies to identify which nutritional, environmental, or lifestyle-related factors should be considered for early intervention and might be useful to reverse the epidemiologic trend.

Early use of inhaled corticosteroids in infancy

The inability to accurately predict the outcome of infants with recurrent wheezy bronchitis makes the early use of inhaled corticosteroids (ICS) controversial. Data from bronchoalveolar lavages and epidemiological surveys suggest a persistent inflammation of the airways in the more severe cases. Prospective studies, mostly with nebulized corticosteroids, have demonstrated clinical efficacy on daytime and nightime symptoms, reduced requirements for rescue bronchodilators and a real steroid sparing effect. In infants with episodic viral-associated wheeze with or without interval symptoms, ICS use carries the risk of overtreatment and of adverse effects. Long-term prospective studies are urgently required to assess the efficacy and safety of ICS and their possible effects on the natural history of infantile asthma.