Footnotes

• Contributors CP retrieved data, carried out the initial analyses, drafted the initial manuscript, reviewed and revised the manuscript, and approved the final manuscript as submitted. MB supervised the retrieving of the data and performed analyses, reviewed and revised the manuscript, and approved the final manuscript as submitted. IC critically reviewed and revised the manuscript, and approved the final manuscript as submitted. EJ-A conceptualised, designed and initiated the study, reviewed and revised the manuscript, and approved the final manuscript as submitted.

• Funding This work is part of: the TINN network (Collaborative Project), supported by the European Commission under the Health Cooperation Work Programme of the 7th Framework Programme (grant agreement no. 223614) and the GRIP network (Network of Excellence (GRiP), supported by the European Commission under the Health Cooperation Work Programme of the 7th Framework Programme (Grant Agreement no 261060).

• Competing interests None.

• Provenance and peer review Not commissioned; externally peer reviewed.