1 From Vanderbilt University School of Medicine, Nashville, TN, USA.
2 the International Epidemiology Field Station, Vanderbilt University Medical Center, Nashville, TN, USA.
3 the Department of Medicine, Division of Epidemiology, Vanderbilt Epidemiology Center, Vanderbilt University, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, TN, USA.