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[Epidemiology of respiratory allergy in children]
I Pin1, C Pilenko-McGuigan, C Cans
1Département de pédiatríe, CHU de Grenoble, France.
Insights
Epidemiology of childhood respiratory allergies is complex due to varied definitions. Key risk factors include genetics, environment, and lifestyle, with prevalence varying globally and increasing in developed nations.
Area of Science:
- Pediatric Allergy and Immunology
- Respiratory Medicine
- Epidemiology
Background:
- Epidemiological studies of pediatric respiratory allergic disorders aim to identify causal and preventive risk factors.
- Lack of consensus on disease definitions complicates cross-study comparisons.
- Atopy is typically defined by positive skin tests, specific IgE, or elevated total IgE levels.
Purpose of the Study:
- To explore the epidemiology of pediatric respiratory allergic disorders.
- To identify risk factors and variations in prevalence across different populations and conditions.
- To highlight challenges in defining and comparing childhood asthma and atopy.
Main Methods:
- Utilized epidemiological approaches to study groups of children under various conditions.
- Employed standardized questionnaires, such as the International Study of Asthma and Allergies in Childhood (ISAAC) study, to assess asthma prevalence.
- Analyzed genetic, sex-related, and environmental factors, including allergen exposure, infections, passive smoking, and pollution.
Main Results:
- Prevalence of asthma and atopy varies significantly worldwide, being lower in Africa and Asia, intermediate in Europe, and high in Anglo-Saxon countries.
- The prevalence of asthma has increased over the past two decades in developed countries.
- Transient and persistent wheezing in infants have distinct risk factors, and childhood asthma is closely linked to atopy.
Conclusions:
- Childhood asthma and atopy are influenced by genetic predisposition, sex, and environmental exposures, including allergen sensitization and lifestyle factors.
- Westernization is associated with increased prevalence of atopy, allergic rhinitis, and asthma.
- Passive smoking is linked to early wheezing, and pollution may aggravate childhood asthma, though its direct role is debated.
Abstract:
Epidemiology of paediatric respiratory allergic disorders allows the approach to causal and preventive risk factors by studying groups or sub groups of children in different locations and under different conditions. This is, however, complicated by the lack of consensus on disease definitions, which renders comparisons between studies difficult. Atopy is usually defined by the presence of positive skin tests (wheal size of at least a mean diameter > or = 3 mm), by the presence of specific IgE, or by the presence of increased total IgE (> or = 100 UI/mL). Infantile asthma is not well defined, complicated by the high prevalence of bronchiolitis; one thus questions between wheezing or wheezy bronchitis. Prevalence is high: among early wheezers, two populations will be defined by the medium term evolution: transient wheezers and persistent wheezers. Risk factors for these two conditions are different. Childhood asthma may be defined by the diagnosis of asthma (specific but fairly non-sensitive), by asthmatic symptoms (wheezing, waking by an attack of shortness of breath) (sensitive but not very specific), or by the combination of symptoms and airway hyperresponsiveness. The ISAAC study has standardised a questionnaire to assess the prevalence of asthma. The preliminary results show that there are wide variations across the world. The prevalence is low in Africa and Asia, intermediate in Europe, and high in Anglo-Saxon countries. The prevalence of asthma has gradually increased over the past 20 years in developed countries. Asthma and atopy are closely associated in children. Risk factors are genetic, associated with sex and environmental factors. Among these, allergic sensitisation is associated with the degree of exposure to allergens. Westernization of way of life is associated with increased prevalence of atopy, allergic rhinitis and asthma. Atopy seems inversely correlated to certain infections. Passive smoking is clearly associated with early wheezing. This and atmospheric pollution aggravate childhood asthma. However, the inducing role of pollution on asthma is still controversial.