Study Characteristics and Quality Assessment
Table S3, S4 summarizes the detailed
characteristics and quality
assessment of all studies, respectively. Most articles were case-control
studies. Geographical location included: Europe (12 studies), America (2
studies), and Asia (1 study). The total number in the 15 studies was
18,813 for cases (having T1DM) and 3,018,809 for controls (not having
T1DM). The prevalence of asthma was 8.51% in the cases and 6.84%, in
the controls. A moderate risk of bias was observed in the NOS
assessment. The selection domain was mostly related to a case-control
design; consecutive or representative sampling was not used. The
exposure domain was assessed using questionnaire, and thus subjected to
recall bias.