Differential effects of age and history of hypertension on regional brain volumes and iron.

Aging affects various structural and metabolic properties of the brain. However, associations among various aspects of brain aging are unclear. Moreover, those properties and associations among them may be modified by age-associated increase in vascular risk. In this study, we measured volume of brain regions that vary in their vulnerability to aging and estimated local iron content via T2* relaxometry. In 113 healthy adults (19-83 years old), we examined prefrontal cortex (PFC), primary visual cortex (VC), hippocampus (HC), entorhinal cortex (EC), caudate nucleus (Cd), and putamen (Pt). In some regions (PFC, VC, Cd, and Pt) age-related differences in iron and volume followed similar patterns. However, in the medial-temporal structures, volume and iron content exhibited different age trajectories. Whereas age-related volume reduction was mild in HC and absent in EC, iron content evidenced significant age-related declines. In hypertensive participants significantly greater iron content was noted in all examined regions. Thus, iron content as measured by T2* may be a sensitive index of regional brain aging and may reveal declines that are more prominent than gross anatomical shrinkage.