1 Donna Spiegelman is with the Department of Biostatistics, Yale School of Public Health, New Haven, CT, and professor emerita in the Departments of Epidemiology, Biostatistics, Nutrition and Global Health, Harvard T. H. Chan School of Public Health, Boston, MA. Xin Zhou is with the Departments of Epidemiology and Biostatistics, Harvard T. H. Chan School of Public Health.