1. Dundee Epidemiology and Biostatistics Unit (T.V., P.T.D.), Division of Population Health Science, Medical Research Institute, University of Dundee, Dundee DD2 4BF, Scotland, United Kingdom
2. Department of Biochemical Medicine (M.J.M.), Dundee DD1 9SY, Scotland, United Kingdom
3. Medical Research Institute (G.P.L.), Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom