White Matter Hyperintensities in Aging and Dementia

Alzheimer's disease (AD) is one of the most devastating international public health epidemics. There are currently no effective disease-modifying or preventative strategies. Current pathogenic models emphasize a single pathway of disease pathogenesis, but underestimate the contribution of small vessel cerebrovascular disease, which manifests primarily as white matter hyperintensities (WMH) on T2-weighted magnetic resonance imaging (MRI). Understanding of the factors that drive the relationship between vascular disease and AD remains elusive; vascular factors may be independent sources of dysfunction that contribute additively to clinical expression, they may interact mechanistically with AD pathology, and/or they may relate to each other because of a shared association with a third set of factors. These issues are particularly relevant among ethnic/racial minorities, who are at much greater risk for clinical AD, have more severe cerebrovascular disease, but appear to have similar levels of AD pathology compared with Whites.

The proposed research examines these factors in a large, longitudinal, multi-ethnic community-based cohort study of older adults in northern Manhattan, New York. The investigators demonstrated that accumulation of WMH, particularly in parietal lobes, predicts incident AD, and is associated with the presence of cerebral microbleeds, an indicator of cerebral amyloid angiopathy. The investigators extend the research to examine mechanistic interactions between cerebrovascular disease and AD. The preliminary data suggest that individuals with evidence of fibrillar amyloidosis have increased parietal lobe WMH and that hemodynamic markers of autoregulatory dysfunction are associated with both WMH and amyloid deposition, which in turn interact to promote the clinical expression of AD. These findings are buffered by new data that establish WMH as a core feature in autosomal dominant forms of AD. In this pilot study, the investigators propose to obtain cross-sectional and longitudinal MRI and amyloid PET data from participants in WHICAP.