From the Stroke Research Group, Clinical Neurosciences, University of Cambridge, United Kingdom (R.L.B., H.S.M.); Division of Health and Social Care Research, Faculty of Life Sciences and Medicine, King's College London, United Kingdom (S.C., C.D.A.W.); National Epidemiology and Surveillance, Canadian Blood Services, Ottawa, Ontario (Q.Y.); School of Medicine and Pharmacology, The University of Western Australia, Perth (G.J.H.); Department of Neurology, Sir Charles Gairdner Hospital, Perth, Australia (G.J.H.); Western Australian Neuroscience Research Institute, Perth (G.J.H.); and Stroke Prevention Research Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom (L.L., P.M.R.). From the Stroke Research Group, Clinical Neurosciences, University of Cambridge, United Kingdom (R.L.B., H.S.M.); Division of Health and Social Care Research, Faculty of Life Sciences and Medicine, King's College London, United Kingdom (S.C., C.D.A.W.); National Epidemiology and Surveillance, Canadian Blood Services, Ottawa, Ontario (Q.Y.); School of Medicine and Pharmacology, The University of Western Australia, Perth (G.J.H.); Department of Neurology, Sir Charles Gairdner Hospital, Perth, Australia (G.J.H.); Western Australian Neuroscience Research Institute, Perth (G.J.H.); and Stroke Prevention Research Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, United Kingdom (L.L., P.M.R.). hsm32@medschl.cam.ac.uk.