Department of Statistics, Northwestern University, 2006 Sheridan Road, Evanston, 60201, USA.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA.|Center for Applied Mathematics, Tianjin University, 92 Weijin Road, Tianjin, 300072, China.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA.|Department of Biostatistics, University of Minnesota, 420 Delaware, Minneapolis, 55455, USA.|Department of Environmental Health, Harvard University, 677 Huntington Avenue, Boston, 02115, USA.|Department of Statistics, Northwestern University, 2006 Sheridan Road, Evanston, 60201, USA.|Department of Environmental Health, Harvard University, 677 Huntington Avenue, Boston, 02115, USA.|Department of Preventive Medicine and Epidemiology, Boston University, 801 Massachusetts Avenue, Boston, 02118, USA.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA.|Department of Preventive Medicine, Northwestern University, 680 N Lake Shore Drive, Chicago, 60611, USA. lei.liu@northwestern.edu.