1. Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, 3300 Thurston Building, Chapel Hill, NC 27599, USA
2. Department of Health Behavior, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
3. Departments of Medicine & Social Medicine, University of North Carolina at Chapel Hill, 333 South Columbia St, MacNider Hall, Chapel Hill, NC 27599, USA.