[1] Harvard Univ, Sch Publ Hlth, Dept Nutr, Boston, MA 02115 USA
[2] Natl Inst Environm Hlth Sci, Epidemiol Branch, NIH, Res Triangle Pk, NC USA
[3] Amer Canc Soc, Epidemiol & Surveillance Res Dept, Atlanta, GA 30329 USA
[4] Massachusetts Gen Hosp, Dept Neurol, Boston, MA 02114 USA
[5] Harvard Univ, Sch Publ Hlth, Dept Epidemiol, Boston, MA 02115 USA