Department of Epidemiology/Biomathematics, The University of Texas Health Center at Tyler 75710, USA.|Department of Epidemiology/Biomathematics, The University of Texas Health Center at Tyler 75710, USA.|Department of Epidemiology/Biomathematics, The University of Texas Health Center at Tyler 75710, USA.|Department of Epidemiology/Biomathematics, The University of Texas Health Center at Tyler 75710, USA.