Data Extraction and Quality Assessment
Two investigators (J.X. and W.L.) extracted the following data from the identified studies: full title, first author, publication year, study design, follow-up period, sources of patient and participant, the number of asthma patients, T1DM patients, and OR/RR/HR with 95%CI. The quality of eligible literature was assessed using the Newcastle-Ottawa Scale (NOS), a tool recommended by the Cochrane Collaboration for the quality assessment of observational studies.12 Eligible studies with scores of 0-3, 4-6, and 7-9 were considered as low, moderate, and high quality, respectively. Disagreements between the investigators in data extraction and quality assessment were resolved by consensus, and if consensus could not be reached, a third investigator (X.Z.) was consulted for a final decision.