Hypertension predicts lower cerebral blood flow and fluid cognitive scores after a lipid challenge in older adults

Background Hypertension (HTN) is a modifiable risk factor for AD. We previously reported an association with high systolic blood pressure (SBP) and lower cerebral blood flow (CBF) using ASL MRI at AAIC 2022. Here we reproduce and expand on those findings in a new cohort of participants. Method After fasting, 29 older adults (age = 66.9±7.3, 20 females) underwent ASL MRI two hours after ingestion of 1/2 cup heavy cream to mimic an oral triglyceride tolerance test (OTTT). At three hours, participants underwent a cognitive assessment using the NIH Toolbox as well as several blood pressure assessments. We used 3D pCASL MRI with background suppression to measure CBF in ml/100g/min using label duration = 1.8 s, post‐labeling delay = 2 s, labeling offset = 25‐30 mm, slices = 30, resolution = 2×2×4 mm3, SENSE‐factor = 2, TR/TE = 5000/18 ms. Finally, we acquired a reference scan (M0, 1 minute) identical to the above scan but with TR = 10,000 ms and no labeling or background suppression. CBF was measured in AD‐vulnerable regions (posterior cingulate, temporal cortex, angular gyrus, and hippocampus). Statistical analyses included Pearson correlation using SAS Studio. Result Overall, SBP tended to drop at one hour following lipid drink and returned to baseline around 2‐3 hours; around 30% of participants had a higher SBP at 2 or 3 hours compared to fasting levels. Systolic but not diastolic blood pressure negatively correlated with global CBF as well as CBF in all four prespecified regions of interest, with strongest correlations at the 3‐hour time point. When the group was split into those with and without HTN (≥130), those with HTN scored lower on fluency composite of NIH Toolbox (110.5±4.3 vs 98.8±3.2, p = 0.037) whereas no differences were noted for the crystallized composite (125.3±4.6 vs 122±3.5, p = 0.58) or MoCA at screening visit (27.9±1 vs 26.7±0.8, p = 0.37). Conclusion Building on our pilot work, we continue to find a strong negative correlation between SBP and CBF. Individuals that met criteria for HTN after ingestion of lipids had lower fluid composite scores on NIH Toolbox, suggesting that maintaining a normal blood pressure helps prevent cognitive decline.