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. 2018 Sep 7;23:44. doi: 10.1186/s12199-018-0734-z

Fig. 1.

Fig. 1

The process of surveying, screening, and selecting the articles for systematic review and meta-analysis based on PRISMA guideline. Ninety-nine studies were identified in the initial search (identification). After the title and abstract screening, 28 studies were excluded (screening). Based on the inclusion and exclusion criteria, 27 studies were excluded from the final analysis (Eligibility). A total of 44 articles were included in meta-analysis