Footnotes

• Contributors LJ collected the data, performed statistical analyses, designed the figures and wrote the first draft of the manuscript. CP and MBdlM supervised the study and participated in data interpretation and writing of the manuscript. All the authors contributed to critical revision of the manuscript, have read and approved its final version. LJ is the guarantor of the study, accepts full responsibility for the work and/or the conduct of the study, has access to the data and controlled the decision to publish.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests LJ, RD and OG have no competing interests. CB-K received personal compensation for consulting, serving on a scientific advisory board, speaking or other activities with Alexion, Biogen, Roche, Merck, Novartis and Sanofi-Genzyme, none related to the present work. EM reports research support from Biogen and ARSEP foundation and personal fees for lectures and advisory boards from Biogen, Janssen, Merck, Novartis, Roche, Sanofi, Teva, none related to the present work. CP reports personal fees from Biogen, Medday, Merck, Novartis, Roche, Sanofi-Genzyme, Teva, none related to the present work. MBdlM has served on scientific advisory boards from Alexion, Biogen, Sanofi, Merck and Novartis and received travel honoraria from Alexion and Novartis, none related to the present work.

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

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