Article History
First Online: 27 May 2019
Compliance with ethical standards
:
: The search strategy, data extraction template along with quality appraisal responses are provided in Electronic Supplementary Material 1, attached to this manuscript. The completed data extraction form is included as Electronic Supplementary Material 2.
: AL contributed to the design of the study, carried out the searches, screening and data extraction, contributed to interpretation of data, and drafted and critically reviewed the paper. EM contributed to the design of the study, carried out the screening and data extraction, contributed to interpretation of data, and drafted and critically reviewed the paper. NL contributed to the design of the study and critically reviewed the paper.
: No funding was received for the writing of this manuscript.
: The authors, AL, EM and NJL, declare that they have no competing interests.