As the elderly population increases, dementia due to Alzheimer's disease (AD) poses an escalating public health threat. Research suggests that there are multiple pathways that lead to the development and expression of AD. Small vessel cerebrovascular disease, visualized on magnetic resonance imaging (MRI) as white matter hyperintensities (WMH), is common in normal aging and is associated with normal age-related cognitive decline. Emerging evidence, however, suggests that cerebrovascular disease may also play a role in the pathogenesis of AD. Work from our laboratory shows that WMH are increased among those at risk for AD; are more severe among patients with AD; and predict the rate of cognitive decline among those with AD. These initial observations strongly indicate that it is essential to demonstrate that longitudinal progression of WMH is related to cognitive decline and incident AD in order to establish causality. The overall aim of this study is to examine how the progression of small vessel vascular disease contributes to cognitive decline and incident AD. This study interfaces with ongoing follow up of the Washington Heights Inwood Columbia Aging Project (WHICAP; P01 AG07232), a community-based epidemiological study of aging and dementia. Beginning in 2003, MRI scans were acquired on a subset of 717 non-demented elderly participants. The current study seeks to re-evaluate these participants with follow up MRI 6 years after their baseline scans. Advanced MRI analysis techniques will be applied to quantify the degree o f WMH change in major neuroanatomical regions. Cerebral microbleeds, a marker of amyloid angiopathy, will also be quantified to explore their association with WMH. The aims include: 1. To examine the longitudinal change in regional WMH with cognitive decline and incident AD. 2. To examine whether severity and WMH change accounts for ethnic group differences in incident AD. 3. To examine the association of WMH distribution and lobar microbleeds, a putative marker of cerebral amyloid angiopathy, among patients with AD and controls. Exploratory aims will examine interrelations among WMH, white matter microstructure, hippocampal volume, and cognition. Findings from this study will clarify the role of small vessel vascular disease in the pathogenesis of cognitive aging and AD, will determine if small vessel vascular disease is a source of ethnic group disparities in AD, and will begin to elucidate the mechanism linking vascular disease to AD.