1. From the Laboratory of Epidemiology and Population Sciences, Intramural Research Program, National Institute on Aging, National Institute of Health, Baltimore, MD (J.E.M., O.M., L.J.L.)
2. Department of Neurology, Feinberg School of Medicine, Northwestern University, Massachusetts General Hospital, Harvard Medical School, Boston (B.S.)
3. Icelandic Heart Association Research Institute, Kópavogur, Iceland (S.S., V.G.)
4. Department of Radiology, Leiden University Medical Center, the Netherlands (M.A.v.B.).
5. University of Iceland, Reykjavik, Iceland (V.G.)