1. Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295 N Martin Ave., Tucson, AZ 85724, USA
2. Department of Family and Community Medicine, College of Medicine, University of Arizona, 1601 N Tucson Blvd., Ste 32, Tucson, AZ 85716, USA