Effects of estrogen replacement therapy on PET cerebral blood flow and neuropsychological performance

Reports that estrogen may protect against age-associated memory decline and Alzheimer's Disease have kindled interest in the effects of estrogen repla cement therapy (ERT) on cognition and brain function. As part of a 9-year s tudy in the Baltimore Longitudinal Study of Aging, we are performing annual magnetic resonance imaging, positron emission tomography (PET), and neurop sychological assessments to examine brain structure and function in individ uals aged 55 and older. PET measurements of regional cerebral blood flow (r CBF) are obtained under 3 conditions: rest and verbal and figural delayed r ecognition memory tasks. Fifteen women receiving ERT (with or without the a ddition of progesterone) were compared with a matched sample of 17 untreate d women. There were no significant differences between groups in regional b rain volumes or ventricular size. However, ERT users and nonusers showed si gnificant differences in PET-rCBF relative activation patterns during the m emory tasks. During verbal memory processing, there were significant intera ctions in rCBF activations for the right parahippocampal gyrus, right precu neus, right frontal regions, and left hypothalamus. During figural memory p rocessing, significant interactions were observed for right parahippocampal and inferior parietal regions and for left visual association and anterior thalamic regions. ERT users also showed better performance on neuropsychol ogical tests of figural and verbal memory and on some aspects of the PET ac tivation tests, although the two groups did not differ in education, overal l verbal ability, or performance on other neuropsychological tests. These f indings confirm our previous observation of the beneficial effects of ERT o n figural memory. Moreover, differences in rCBF activation patterns between ERT users and nonusers suggest an area for future research to examine mech anisms through which ERT may influence memory and other cognitive abilities , (C) 1998 Academic Press.