1. Department of Neurology; Wake Forest School of Medicine, Medical Center Boulevard; Winston-Salem North Carolina 27157-1078 USA
2. Center for Worker Health; Wake Forest School of Medicine; Winston-Salem North Carolina USA
3. Department of Biostatistical Sciences; Division of Public Health Sciences; Wake Forest School of Medicine; Winston-Salem North Carolina USA
4. Department of Family and Community Medicine; Wake Forest School of Medicine; Winston-Salem North Carolina USA
5. Department of Neurology School of Medicine; Catholic University of Daegu; Daegu South Korea
6. Department of Public Health Education; University of North Carolina at Greensboro; Greensboro North Carolina USA
7. Department of Epidemiology and Prevention; Division of Public Health Sciences; Wake Forest School of Medicine; Winston-Salem North Carolina USA