1. Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
2. Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, USA
3. Department of Epidemiology, Johns Hopkins University, Baltimore, MD, USA
4. National Heart Lung and Blood Institute, Bethesda, MD, USA
5. Department of Neurology, Mayo Clinic, Rochester, MN, USA
6. Center of Biostatistics and Bioinformatics, University of Mississippi Medical Center, Jackson, MS, USA
7. Department of Medicine, University of Mississippi Medical Center, Jackson, MS, USA