Text and Data Mining valid from 2018-08-02
Received: 18 January 2018
Accepted: 26 July 2018
First Online: 2 August 2018
Compliance with ethical standards
: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
: Ethical approval was not needed for this meta-analysis.
: Informed consent was not required for this meta-analysis.