[1] Univ London Imperial Coll Sci Technol & Med, Hammersmith Hosp, Natl Heart & Lung Inst, London W12 0NN, England
[2] Univ London Imperial Coll Sci Technol & Med, Dept Epidemiol & Publ Hlth, London W2 1PG, England
[3] Univ Michigan, Ctr Stat Genet, Ann Arbor, MI 48109 USA
[4] Univ London Imperial Coll Sci Technol & Med, Hammersmith Hosp, Sect Genom Med, London W12 0NN, England