Asian birth cohort studies on allergic diseases: The A2BC network initiative

The Asia Allergy Birth Cohort (A2BC) network consolidates data from multiple independently established birth cohorts across Asia to enhance research on host–environment interactions in allergic diseases. These cohorts, established at different times with various methodologies, are reliable data sources. Our aim is to introduce the content, variables, and outcomes of these cohorts while highlighting their differences, laying the groundwork for future collaborative research. The A2BC network includes 10 cohort studies on allergic diseases from six Asian countries. Enrollment criteria, study aims, and an initial inventory were discussed and confirmed through five business meetings. A common database was developed to assess the study characteristics of these observational cohorts on allergic diseases, though harmonization efforts are retrospective. Five studies collected data on specific immunoglobulin E responses to various inhalant and food allergens, while six cohorts conducted skin prick tests. Lung function measurements were included in some studies, but without standardized procedures across cohorts. Asthma and allergic rhinitis were primarily assessed using questionnaires or doctor diagnoses, while assessments of eczema and food allergies varied across studies. The A2BC network also examines early‐life environmental factors such as delivery mode, antibiotic usage, diet, and air pollutants, although these exposures were measured differently across the cohorts. Despite differences in the origins, methods, and objectives of each cohort, pooling data and conducting joint analyses offer valuable insights into the relationship between environmental exposures and allergic disease outcomes in Asian children. This approach can serve as a foundation for future collaborative research.