1. Division of Population Medicine, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4YS, U.K. farewelld@cf.ac.uk
2. Centre for Trials Research, College of Biomedical and Life Sciences, Cardiff University, Heath Park, Cardiff CF14 4YS, U.K. huangc12@cf.ac.uk
3. Leibniz Institute for Prevention Research and Epidemiology – BIPS, Achterstraße 30, 28359 Bremen, Germany didelez@leibniz-bips.de