A systematic literature search of MEDLINE, EMBASE, and Scopus was undertaken to identify original studies stating the incidence of CES, and the estimates were combined in a meta-analysis as described in the protocol registered with PROSPERO (registration no. CRD42017065865) and reported using the PRISMA guidelines.



MEDLINE
A systematic literature search of MEDLINE, EMBASE, and Scopus was undertaken to identify original studies stating the incidence of CES, and the estimates were combined in a meta-analysis as described in the protocol registered with PROSPERO (registration no. CRD42017065865) and reported using the PRISMA guidelines.



EMBASE
A systematic literature search of MEDLINE, EMBASE, and Scopus was undertaken to identify original studies stating the incidence of CES, and the estimates were combined in a meta-analysis as described in the protocol registered with PROSPERO (registration no. CRD42017065865) and reported using the PRISMA guidelines.



Scopus
A systematic literature search of MEDLINE, EMBASE, and Scopus was undertaken to identify original studies stating the incidence of CES, and the estimates were combined in a meta-analysis as described in the protocol registered with PROSPERO (registration no. CRD42017065865) and reported using the PRISMA guidelines.



PROSPERO
A systematic literature search of MEDLINE, EMBASE, and Scopus was undertaken to identify original studies stating the incidence of CES, and the estimates were combined in a meta-analysis as described in the protocol registered with PROSPERO (registration no. CRD42017065865) and reported using the PRISMA guidelines.



PRISMA