Contribution to authorship
Jing Han, Hao Lv and Zhe Wang wrote the protocol. Zhe Wang performed the search. Hao Zheng, Zhe Wang and Yanan Li independently selected eligible studies and extracted data. Differences of opinion were registered and resolved by consensus with Jing Han. Zhe Wang and Hao Zheng performed the meta-analyses. Yanan Li, Hao Zheng and Zhe Wang participated in the interpretation of the data and writing of the review