1. Center for Health Policy, Sanford Duke School of Public Policy, Duke University, Durham, NC, USA
2. Department of Community and Family Medicine, Duke University Medical Center, Durham, NC, USA
3. Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
4. Institute for Social Research, University of Michigan, Ann Arbor, MI, USA
5. Program in Epidemiology of Dementia, Duke University Medical Center, Durham, NC, USA