Effect of hypertension on the resting-state functional connectivity in patients with Alzheimer's disease

Abstract

Background: Although hypertension (HTN) is well known to be a risk factor for Alzheimer’s disease (AD), the effects of HTN on brain function in AD patients are not well understood. We investigated alterations in resting-state functional connectivity according to the presence of HTN in AD patients by using a method of correlation analysis based on a seed region in the posterior cingulate cortex (PCC). We also determined whether differences in resting-state connectivity were associated with gray matter (GM) atrophy.Methods: Thirty-seven AD patients (18 with HTN group and 19 with non-HTN) underwent the resting-state functional magnetic resonance imaging. We obtained the posterior cingulate cortex (PCC) maps by a temporal correlation method, to identify alterations in the functional connectivity of the PCC in HTN group relative to non-HTN group. A temporal correlation method was used to build PCC connectivity maps. Voxel-based morphometry analysis was also applied to adjust the confounding effect of GM atrophy.Results: We detected a decreased connectivity to the PCC in the regions of subgenual anterior cingulated cortex (ACC) in HTN group relative to non-HTN group. However, we observed a pattern of increased connectivity between the PCC and the left inferior parietal cortex (IPC) in HTN group. After correction for GM atrophy, all detected regions still remained significant.Conclusion: The decreased subgenual ACC and increased left IPC connectivity to the PCC seen in AD patients with HTN suggests the possibility that HTN impairs resting-state functional connectivity of the AD brain, inducing a compensational process outside the impaired networks. This finding may account for an additional contribution of HTN to the pathophysiology of AD.