1. University of Pittsburgh, Graduate School of Public Health, Department of Epidemiology, Center for Aging and Population Health, Pittsburgh, PA 15213,USA
2. University of Pittsburgh, School of Medicine, Division of Geriatric Medicine, Pittsburgh, PA 15261, USA
3. Department of Biostatistics, Boston University School of Public Health, Boston, MA 02118, USA
4. Division of Geriatrics, Department of Medicine, Boston University Medical Center, Boston, MA 02118, USA
5. The Gertrude H. Sergievsky Center and the Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY 10032, USA
6. The Danish Aging Research Centre, Epidemiology, University of Southern Denmark, Odense, Denmark
7. National Institutes of Health, National Institute on Aging, Bethesda, MD 20892, USA
8. Johns Hopkins Medical Institutions, Bayview Medical Center, Baltimore, MD 21224, USA
9. Duke University, Center for Demographic Studies, Durham, NC 27708