1. From Academic Units of Pathology (J.E.S., O.H., S.B.W., M.S.F., G.F., C.E.L., P.G.I.) and Neurology (P.R.H., H.H., P.J.S.), University of Sheffield, Sheffield, UK; MRC Biostatistics Unit (F.M.), Institute of Public Health, Cambridge, UK; Institute for Health and Ageing (J.T.O., R.B., R.N.K.), University of Newcastle upon Tyne, UK; Department of Public Health and Primary Care (C.B.), University of Cambridge, Cambridge, UK.