1. a Department of Public Health , Brody School of Medicine, East Carolina University , Greenville, North Carolina, USA
2. b Department of Medicine , University of California, San Francisco , San Francisco, California, USA
3. c University of North Carolina at Chapel Hill, Gillings School of Global Public Health, Department of Epidemiology , Chapel Hill, North Carolina, USA
4. d University of North Carolina at Chapel Hill, Center for Health Promotion and Disease Prevention and Gillings School of Global Public Health, Department of Nutrition , Chapel Hill, North Carolina, USA