1. Department of Medicine; Feinberg School of Medicine; Northwestern University; Chicago; Illinois
2. Department of Preventive Medicine; Feinberg School of Medicine; Northwestern University; Chicago; Illinois
3. Laboratory of Clinical Epidemiology; National Institute on Aging; Bethesda; Maryland
4. Laboratories of Epidemiology, Demography, and Biometry; National Institute on Aging; Bethesda; Maryland
5. Department of Family and Preventive Medicine; University of California at San Diego; San Diego; California
6. Stanford University; Palo Alto; California
7. Department of Neurology; Feinberg School of Medicine; Northwestern University; Chicago; Illinois