Hypertension and race affect cerebral blood flow and cognition in older adults without dementia

Background It is known that African Americans have a higher prevalence of AD than white Americans, but it is not fully understood why this is the case. One potential explanation is that African Americans also have a higher prevalence of cardiovascular risk factors, which also confer a risk for AD. Racial differences in several AD‐specific and cardiovascular disease biomarkers have been reported, but these findings are generally not conclusive. In addition, very few papers have assessed racial differences in cerebral blood flow (CBF), an important noninvasive biomarker for AD/dementia. We investigated the relationships between cerebral blood flow (CBF), race and hypertension in a cohort of older individuals without dementia. Method Participants included 116 older individuals, 21 (18%) African American, who were cognitively normal (CN), had subjective cognitive decline (SCD), or had mild cognitive impairment (MCI). 3D pseudo‐continuous arterial spin label (pCASL) MRI on a Prisma 3T and cardiovascular risk factors and cognitive domain z‐scores from the time of scan were analyzed. Multiple regression was used to assess the relationships between race, hypertension, and CBF on a region‐of‐interest and voxel‐wise basis with age, sex, diagnostic group and total grey matter volume as covariates. Result Region‐of‐interest and voxel‐wise CBF was decreased in African Americans and in individuals with hypertension. While there was overlap between the affected regions, especially temporal lobes, hypertensive individuals also had decreased CBF in anterior brain regions, while African Americans had decreased CBF in posterior brain regions. The effect of race on CBF remained after hypertension was included as a covariate. Despite the regional overlap, there was no interaction of race and hypertension on CBF. Perfusion in affected brain regions was positively correlated with attention in all participants, as well as with visuospatial function in African Americans. Conclusion Hypertensive individuals and African Americans have decreased CBF in partially overlapping brain regions. Decreased CBF in these regions was differentially associated with cognitive function according to race. Further study of CBF in larger diverse samples is warranted.