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

Background/objectives: Although hypertension is known to be a risk factor for AD, the effects of hypertension on brain function in AD patients are not well understood. We investigated alterations in resting-state functional connectivity according to the presence of hypertension 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 atrophy.
Methods: Thirty-seven AD patients (18 patients with hypertension and 19 patients without hypertension) underwent the resting-state functional magnetic resonance imaging. We obtained the PCC maps by a temporal correlation method, to identify alterations in the functional connectivity of the PCC in hypertensive group relative to non-hypertensive group. Voxel-based morphometry analysis was also applied to adjust the confounding effect of gray matter atrophy.
Results: We detected a decreased connectivity to the PCC in the regions of subgenual anterior cingulated cortex (ACC) in hypertensive group relative to non-hypertensive group. However, we observed a pattern of increased connectivity between the PCC and the left inferior parietal cortex in hypertensive group. After correction for gray matter atrophy, all detected regions still remained significant.
Conclusions: Altered connectivity in AD patients with hypertension suggests the possibility that hypertension impairs resting-state functional connectivity of the AD brain, inducing a compensational process outside the impaired networks or disequilibrium in brain connectivity. This finding may account for an additional contribution of hypertension to the pathophysiology of AD.
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