Material and Method: Schoolchildren, aged 6 to 18 years, were randomly selected from six schools in central Bangkok. Parents of the children completed a questionnaire. Standard spirometry was performed. Children were classified as having airflow obstruction if FEV1/FVC ratio was < 0.8. Children with FEV1/FVC ratio ≥ 0.8, matched by sex, age, weight, and height, were randomly selected and classified as having no airflow obstruction. Risk factors were identified by univariate and multivariate analyses.

Results: Among 1,065 children assessed by spirometry, 43 (4%) demonstrated airflow obstruction. Only three factors including wheezing apart from cold in the past 12 months (OR, 12.82; 95% CI, 1.3-126.5), family history of allergic rhinitis (OR, 2.54; 95% CI, 1.21-5.32), and starting infant formula since birth (OR, 2.47; 95% CI, 1.21-5.04) were shown to be significant risk factors associated with airflow obstruction.

Conclusion: The prevalence of airflow obstruction in schoolchildren is lower than those reported in most adult studies. Asthma and family history of allergic rhinitis are important risk factors associated with airflow obstruction. Exclusively breastfeeding since birth might be another helpful measure to prevent the development of airflow obstruction in children.

Keywords: Airflow obstruction, Spirometry, Children, Asthma, Allergy, Breastfeeding