Patterns of regional cerebral blood flow associated with low hemoglobin in the Baltimore Longitudinal Study of Aging

Abstract

Background: Anemia has been associated with elevated cerebral blood flow (CBF) in animal models and certain clinical conditions (eg, renal disease), but whether hemoglobin level variations across a relatively normal range are associated with local or diffuse CBF changes is unclear. We investigated whether lower hemoglobin is associated with regional increases in relative CBF in older individuals, and if these increases occur in watershed regions.

Methods: Seventy-four older nondemented adults underwent serial (15)O water positron emission tomography scans. Voxel-based analysis was used to investigate regional relative CBF patterns in association with hemoglobin level and in individuals with and without anemia. Analyses of cross-sectional relations between regional CBF and anemia were performed separately at two time points, 2 years apart, to identify replicable patterns of associations.

Results: Restricting results to associations replicated across two cross-sectional analyses, lower hemoglobin was associated with higher relative CBF within the middle/inferior frontal, occipital, precuneus, and cerebellar regions. In addition, individuals with anemia (n = 15) showed higher relative CBF in superior frontal, middle temporal, hippocampal, and gyrus rectus regions than those without anemia. In some regions (right superior temporal gyrus, left inferior frontal gyrus, midline cuneus, and right precuneus); however, lower hemoglobin was associated with lower relative CBF.

Conclusions: In nondemented individuals, lower hemoglobin is associated with elevated relative CBF in specific cortical areas but reduced CBF in other areas. Whether this association between anemia and CBF in the absence of chronic diseases and in a normal physiologic range is related to clinical endpoints warrants further study.

Figure 1.

Correlations between hemoglobin and regional cerebral blood flow (rCBF) in older adults, replicated at two time points. Analysis is adjusted for age and sex. Red regions represent areas where increased rCBF is associated with decreased hemoglobin; blue regions represent areas where decreased rCBF is associated with decreased hemoglobin. Z levels indicate the axial level of the brain slices.

Figure 2.

Differences in regional cerebral blood flow (rCBF) in older adults with and without anemia, replicated at two time points. See figure 1 legend.