We request an administrative supplement for the purpose of conducting analyses of trends in the population prevalence of cognitive impairment and dementia using data from the HRS. Tracking the population prevalence of cognitive impairment and dementia is a key public health and public policy priority given the wide-ranging impact that dementia has on the growing number of older adults, their families, and public programs such as Medicare and Medicaid. The high priority of tracking dementia trends, as well as the potential demographic and medical factors associated with either rising or declining dementia risk, was made explicit in the 2011 National Alzheimer?s Project Act (NAPA). We believe that the HRS is the most valuable dataset currently available to better understand and track the prevalence of dementia in the US population. The proposed will allow us to update prior HRS work in this area, as well as begin to develop new methods and collaborations that will increase our ability to use the HRS for tracking the impact of dementia in the United States, as well as comparing US dementia prevalence to other countries around the world.