[1] BRIGHAM & WOMENS HOSP, BOSTON, MA 02115 USA
[2] UNIV QUEENSLAND, DEPT SOCIAL & PREVENT MED, BRISBANE, QLD 4000, AUSTRALIA
[3] HARVARD UNIV, SCH MED, DEPT PREVENT MED, BOSTON, MA 02115 USA
[4] HARVARD UNIV, SCH MED, DEPT CLIN EPIDEMIOL, BOSTON, MA 02115 USA
[5] HARVARD UNIV, SCH PUBL HLTH, DEPT EPIDEMIOL, BOSTON, MA 02115 USA
[6] HARVARD UNIV, SCH MED, CHANNING LAB, DEPT MED, BOSTON, MA 02115 USA