3.2 Study Characteristic
Six cross-sectional studies and one prospective cohort study, with 20456 subjects were included for the final meta-analysis. The sample size of the studies ranged from 16 to 18912. The age of participants ranged from 3 to 15 across all studies. Outcomes in the studies are showed as follows: asthma exacerbation, asthma admissions, emergency room visits, use of inhaled corticosteroids and use of Beta-2 agonists
The main characteristics of the 7 articles were summarized in Table 1. AHRQ scores suggested that all studies scored at eight to nine as high quality.