Footnotes

• Contributors JFL and GE conceived and designed the study with input from the other authors. JFL, GE and HH collected the data. JFL and GE jointly wrote the first draft of the paper, supervised the project and funded this study. GE and AS analysed the data. All authors interpreted the data and contributed to the writing of the paper. All authors revised and approved the final version.

• Funding All authors have completed the International Committee of Medical Journal Editors uniform disclosure form at http://www.icmje.org/coi_disclosure.pdf and declare (that) this project was supported by grants from the Swedish Society of Medicine and the Stockholm County Council. The assembly of the Scandinavian Donations and Transfusions database 2 was made possible through grants from the Swedish research council (2011-30405, 2007-7469), the Swedish Heart-Lung Foundation (20090710), the Swedish Society for Medical Research (Edgren), the strategic research programme in epidemiology at Karolinska Institutet and the Danish Council for Independent Research (2009B026).

• Disclaimer This manuscript represents the views of the authors.

• Competing interests None declared.

• Ethics approval This project (2016/940-31/1) was approved by the Ethics Review Board in Stockholm, Sweden on 20 June 2016.

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

• Data sharing statement Other researchers can apply for our data through the Swedish National Board of Health and Welfare.

• Transparency The lead author affirms that this manuscript is an honest, accurate and transparent account of the study being reported; that no important aspects of the study have been omitted and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.