Vascular factors resulting in cerebrovascular disease are related to cognitive decline in individuals without neurodegenerative disease. In particular, multiple studies have found associations between stroke risk factors and impairments in memory [1
] and executive functions [1
]. Some studies have additionally demonstrated that stroke risk factors such as high blood pressure and diabetes can lead to general cognitive impairment [2
] and dementia [7
]. The specific causes of cognitive impairment resulting from cerebrovascular disease are unknown, but one potential marker of the resulting neuropsychological impairment is damage to subcortical white matter tracks seen on MRI in clinically asymptomatic individuals as white matter hyperintensities (WMH).
WMH are associated with decrements in cognitive functions associated with the frontal lobes including psychomotor speed, attention, and organization as well as with memory functions [9
]. One study that examined regional white matter and cognitive performance over the adult lifespan demonstrated that frontal white matter was associated with tasks of memory and executive functioning, and that the relation between age and neuropsychological performance may be mediated by frontal lobe white matter [17
Few studies, however, have examined the association of white matter changes and cognitive impairment in ethnic minority cohorts, despite evidence that some groups may present with greater vascular risk factors implicating the possibility of more severe vascular pathology and resulting cognitive impairment in those groups [18
]. One recent study based on an ethnic minority cohort did examine WMH and cognition and found that WMH volume significantly predicted performance on tasks of psychomotor functioning and cognitive flexibility [19
]. This study included individuals from Caucasian, Hispanic and African American ethnicities. However, the study only examined the association of WMH to executive functioning and not to other neuropsychological domains such as memory and visuospatial functioning. In addition, the ethnic minority groups were combined in all analyses despite the differential stroke risk factors that have been found in African American, Hispanic, and Caucasian individuals [20
]. Another study that examined WMH in African-Caribbean individuals in comparison to Caucasians found that the African-Caribbean participants exhibited greater parieto-occipital white matter lesion volumes and also displayed poorer performance on tests of executive function [21
]. This study was also limited by using a single ethnic minority cohort and only examining performance on a task of executive function despite evidence of a more widespread influence of WMH on cognition.
The current study examines an extension of the original Framingham Heart Study Offspring cohort, which was predominantly Caucasian and reflected the population of Framingham, Mass., USA, at the time of the enrollment of the original Framingham study cohort. In the last decade, there has been an effort to recruit ethnically diverse participants in order to examine the generalizability of the reports that were based on the predominantly Caucasian cohort. Therefore, the aim of this study is to determine whether previously reported associations between brain volume, WMH, and neuropsychological test performance apply to the ethnic minority cohort of the Framingham Heart Study.