1. School of Nursing, Duke University, Durham, NC 27710, USA; Durham VA Medical Center, Durham, NC 27705, USA
2. Division of Multiple Sclerosis & Neuroimmunology, Department of Neurology, Michigan Medicine, Ann Arbor, MI 48109, USA
3. Applied Biostatistics Laboratory, School of Nursing, University of Michigan, Ann Arbor, MI 48109, USA
4. School of Public Health, University of Michigan, Ann Arbor, MI 48109, USA
5. School of Medicine, Duke University, Durham, NC 27710, USA
6. School of Nursing, University of Michigan, Ann Arbor, MI 48109, USA