1. Centre for Global Health Research, Usher Institute of Population Health Sciences and Informatics, The University of Edinburgh, Edinburgh EH8 9AG, United Kingdom
2. Colon Cancer Genetics Group, Medical Research Council Human Genetics Unit, Medical Research Council Institute of Genetics & Molecular Medicine, Western General Hospital, The University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
3. Stanford Prevention Research Center, Departments of Medicine and Health Research and Policy, Stanford University School of Medicine, Stanford, California 94305-5411;
4. Department of Statistics, Stanford University School of Humanities and Sciences, Stanford, California 94305-5411