This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [
8]. We performed a search for relevant literature in the PubMed, Embase and Cochrane Central Register of Controlled Trials databases for randomized controlled trials (RCTs) conducted between January 1990 and October 2016. The search strategy did not include restrictions on language or race, and the search was performed using the following key words in Embase: ‘diabetes mellitus, insulin-dependent’:ab,ti OR ‘diabetes mellitus, insulin dependent’:ab,ti OR ‘insulin-dependent diabetes mellitus’:ab,ti OR ‘diabetes mellitus, insulin-dependent, 1’:ab,ti OR ‘diabetes mellitus, juvenile-onset’:ab,ti OR ‘diabetes mellitus, juvenile onset’ OR ‘juvenile-onset diabetes mellitus’:ab,ti OR ‘type 1 diabetes mellitus’:ab,ti OR ‘diabetes mellitus, sudden-onset’:ab,ti OR ‘diabetes mellitus, sudden onset’:ab,ti OR ‘mellitus, sudden-onset diabetes’:ab,ti OR ‘sudden-onset diabetes mellitus’:ab,ti OR ‘diabetes mellitus, type i’:ab,ti OR ‘iddm’:ab,ti OR ‘insulin-dependent diabetes mellitus 1’:ab,ti OR ‘insulin dependent diabetes’ OR ‘juvenile-onset diabetes mellitus 1’:ab,ti OR ‘diabetes, juvenile-onset’:ab,ti OR ‘juvenile onset diabetes’:ab,ti OR ‘diabetes mellitus, brittle’:ab,ti OR ‘brittle diabetes mellitus’:ab,ti OR ‘diabetes mellitus, ketosis-prone’:ab,ti OR ‘diabetes mellitus, ketosis prone’:ab,ti OR ‘ketosis-prone diabetes mellitus’:ab,ti OR ‘diabetes, autoimmune’:ab,ti AND ‘glucagon like peptide 1’:ab,ti OR ‘glucagon-like peptide-1’:ab,ti OR ‘glp-1’:ab,ti OR ‘glp 1’:ab,ti OR ‘exenatide’:ab,ti OR ‘liraglutide’:ab,ti OR ‘lixisenatide’:ab,ti OR ‘albiglutide’:ab,ti OR ‘semeglutide’:ab,ti OR ‘incretin’:ab,ti OR ‘glucagon like peptide-1’:ab,ti OR ‘byetta’:ab,ti OR ‘bydureon’:ab,ti OR ‘victoza’:ab,ti OR ‘saxenda’:ab,ti OR ‘lyxumia’:ab,ti OR ‘tanzeum’:ab,ti OR ‘dulaglutide’:ab,ti OR ‘trulicity’:ab,ti OR ‘taspoglutide’:ab,ti AND ‘insulin, regular’:ab,ti OR ‘regular insulin’:ab,ti OR ‘soluble insulin’:ab,ti AND ‘insulin, soluble’:ab,ti OR ‘insulin a chain’:ab,ti OR ‘sodium insulin’:ab,ti OR ‘insulin, sodium’:ab,ti OR ‘novolin’:ab,ti OR ‘iletin’:ab,ti OR ‘insulin b chain’:ab,ti OR ‘chain, insulin b’:ab,ti AND ‘randomized controlled trial’ OR ‘placebo’ OR ‘randomized.’ We searched all potentially eligible papers for inclusion in the meta-analysis.