Text and Data Mining valid from 2019-06-10
First Online: 10 June 2019
Compliance with Ethical Standards
: No sources of funding were received for the preparation of this study.
: Dawei Shi, Ziye Zhou, Ying Dai, Xiaofeng Pan, Qinqin Cao have no conflicts of interest that are directly relevant to the content of this systematic review and meta-analysis.
: Guarantor of the article: Dawei Shi.
: DS and ZZ designed the study, then screened titles and abstracts resulting from the search. YD and QC involved in the data extraction. DS performed the statistical analysis, interpreted the results and wrote the draft. XP helped with language editing and critically revised the manuscript.