Bei Wu is with the Center on Aging, West Virginia University, Morgantown, and the Department of Community Medicine, West Virginia University, Morgantown. Brenda L. Plassman is with the Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC. Jersey Liang is with the Department of Health Management and Policy, University of Michigan, Ann Arbor. Liang Wei is with the Center on Aging, West Virginia University, Morgtantown.