Received: 25 October 2019
Accepted: 20 December 2019
First Online: 3 January 2020
Ethics approval and consent to participate
: Not applicable<b>.</b> Ethical approval will not be required for this systematic review and meta-analysis as only a secondary analysis of data already available in scientific databases will be conducted.
: Not applicable. The manuscript will not contain data from any individual person.
: The authors declare that they have no competing interests.