1. Neurology Unit, Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
2. Department of Statistics and Operations Research, College of Science, King Saud University, Riyadh, Saudi Arabia
3. Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
4. Department of Medicine, Geriatric Division, University of British Columbia, Vancouver, Canada