INTERACTION OF RESTING CEREBRAL BLOOD FLOW AND COGNITION IN COGNITIVELY NORMAL OLDER ADULTS: EFFECT OF APOE EPSILON4 ALLELE

Abstract

The apolipoprotein E (ApoE) ε4 allele is related to increased risk for developing Alzheimer's disease (AD). It has been suggested that ApoE is likely involved in the maintenance of cognitive function through regulating the function of cerebrovascular systems. This study investigated whether ApoE genotype modified the relationship between voxel-wise CBF and cognitive function in a group of cognitively normal older adults. Thirty cognitively intact older adults (13 ApoE ε4 carriers and 17 noncarriers) were included in this study. The groups were matched in mean age, years of education, gender distribution, vascular risk burden, and scores on the Geriatric Depression Scale. All participants were tested with a comprehensive cognitive battery and underwent arterial spin labeling magnetic resonance imaging to investigate their resting cerebral blood flow. Compared to the ApoE ε4 noncarrier group, the ε4 carrier group has shown increased CBF in frontal regions. Moreover, significant interactions between ApoE genotype and cognition (i.e., memory and executive function composite scores) on CBF were found in frontal, parietal, and temporal regions. A consistent pattern of positive associations between CBF and cognitive function was observed in the ε4 carrier group, but not in the noncarrier group. Genetic risk factors for the development of AD may involve increases in resting CBF in an effort to compensate for altered metabolism and/or increased demand for oxygen and glucose due to compensatory changes in neuronal activity.