1. Department of Epidemiology; College of Public Health; University of Arkansas for Medical Sciences; Little Rock Arkansas U.S.A
2. Department of Neurology; Weill Cornell Medical College; Methodist Neurological Institute; Houston Texas U.S.A
3. Division of Biostatistics, and Michael & Susan Dell; Center for Healthy Living; University of Texas School of Public Health; Austin Texas U.S.A
4. Departments Neurology and Epidemiology; Gertrude H. Sergievsky Center; Columbia University; New York New York U.S.A