[1] Univ Aberdeen, Sch Med & Dent, Div Appl Hlth Sci, Aberdeen AB25 2ZD, Scotland
[2] Univ Manchester, Cardiovasc Inst, Manchester, Lancs, England
[3] Univ Cambridge, Dept Publ Hlth & Primary Care, Clin Gerontol Unit, Cambridge, England
[4] MRC Epidemiol Unit, Cambridge, England