Chronic diseases, which increase in prevalence with age, impair intellectual functioning. It has been shown that patients with essential hypertension have impaired performance on neuropsychological tests relative to age-matched controls. The mechanism by which hypertension impairs intellectual function is unknown. A likely possibility is that hypertension induces changes in the cerebral vasculature which are responsible for the neuropsychological impairments. Hypertension induces morphological changes (vascular remodeling) which may interfere with regional cerebral blood flow (rCBF) responses induced by information processing. Positron Emission Tomography (PET) functional brain imaging permits the investigators to test the hypothesis that hypertension impairs the rCBF response. With the advent of ultrasound measurements of the carotid arteries, the investigators can also test a second hypothesis that atherosclerosis influences intellectual function. This second hypothesis is considered because of the results available from the Kuopio Ischemic Heart Disease Study. Extent of carotid atherosclerosis was negatively related to intellectual functioning. Given that atherosclerosis could not be assessed in earlier studies of hypertension, it may be that only atherosclerosis is uniquely associated with intellectual impairments. Alternatively, heightened blood pressure and atherosclerosis may independently or interactively induce impairment. The investigators propose a project to test the hypothesis that hypertension alters neuropsychological function by damping the rCBF response to metabolic need created during information processing; and that carotid atherosclerosis adds to these impairments via the same mechanism. Measures of white matter lesions are also obtained to see if these may mediate the influences of hypertension and atherosclerosis. The hypothesis is tested by computing the contribution that hypertension and carotid atherosclerosis make directly and interactively to neuropsychological performance and rCBF in selected regions activated by performance tasks. The project attempts to identify mechanisms for how diseases of aging influence intellectual functioning. Successful completion will clarify a) how aging and the diseases of aging reduce intellectual functioning, and b) ultimately permit a rational choice of clinical regimen to treat the diseases of aging while minimizing neuropsychological side effects.
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