[1] Univ Surrey, Guildford GU2 5XH, Surrey, England
[2] Carlos III Inst Hlth, Madrid, Spain
[3] Consortium Biomed Res Epidemiol & Publ Hlth, Madrid, Spain
[4] Johns Hopkins Univ, Baltimore, MD 21218 USA
[5] Univ Warwick, Sch Med, Coventry CV4 7AL, W Midlands, England