[1] Framingham Heart Dis Epidemiol Study, Framingham, MA USA
[2] NHLBI, Cardiovasc Epidemiol & Human Genom, NIH, Bethesda, MD 20892 USA
[3] Boston Univ, Sch Publ Hlth, Dept Biostat, Boston, MA USA
[4] Univ Bristol, Sch Social & Community Med, Bristol, Avon, England
[5] Univ Bristol, Sch Clin Sci, Bristol, Avon, England