Disease Burden Affects Aging Brain Function

Abstract

Background: Most older adults live with multiple chronic disease conditions, yet the effect of multiple diseases on brain function remains unclear.

Methods: We examine the relationship between disease multimorbidity and brain activity using regional cerebral blood flow (rCBF) 15O-water PET scans from 97 cognitively normal participants (mean baseline age 76.5) in the Baltimore Longitudinal Study of Aging (BLSA). Multimorbidity index scores, generated from the presence of 13 health conditions, were correlated with PET data at baseline and in longitudinal change (n = 74) over 5.05 (2.74 SD) years.

Results: At baseline, voxel-based analysis showed that higher multimorbidity scores were associated with lower relative activity in orbitofrontal, superior frontal, temporal pole and parahippocampal regions, and greater activity in lateral temporal, occipital, and cerebellar regions. Examination of the individual health conditions comprising the index score showed hypertension and chronic kidney disease individually contributed to the overall multimorbidity pattern of altered activity. Longitudinally, both increases and decreases in activity were seen in relation to increasing multimorbidity over time. These associations were identified in orbitofrontal, lateral temporal, brainstem, and cerebellar areas.

Conclusion: Together, these results show that greater multimorbidity is associated with widespread areas of altered brain activity, supporting a link between health and changes in aging brain function.

Keywords: Brain activity; Health; Imaging; MRI; PET.

Figure 1.

Multimorbidity and brain function. Regions where higher multimorbidity scores correlated with levels of brain activity measured by rCBF (p < .005, >50 voxels) are shown on sagittal slices beginning in the left and progressing through the right hemisphere. Regional patterns are shown at baseline and in longitudinal change over time. Blue represents regions of lower baseline or decreased longitudinal activity; orange represents regions of higher or increased activity.

Figure 2.

Contributions of individual disease components at baseline. Of the 3 index components examined, hypertension and chronic kidney disease showed individual contributions to the multimorbidity pattern observed at baseline. Significant regional correlations are circled in green. Lower brain activity is indicated in blue, and higher activity in orange.