Regional brain iron mapping in obstructive sleep apnea adults

Obstructive sleep apnea (OSA) subjects show significant white matter injury, including myelin changes in several brain areas, potentially from impaired glial cells, contributing to increased iron levels that escalate neurodegeneration, but brain iron loads are unclear. Our aim was to examine regional brain iron load, using T2∗-relaxometry, in OSA adults before and after continuous positive airway pressure (CPAP) treatment over controls.

We performed T2∗-weighted imaging using a 3.0-T MRI scanner on 35 OSA adults, who were followed after 3- and 9- mo CPAP treatment, and 67 controls. Using T2∗-weighted images, R2∗maps were calculated, normalized, and smoothed. The smoothed R2∗ maps, as well as average R2∗ values extracted from different brain regions were compared between OSA and controls using ANCOVA (covariates: age and sex) and paired t-tests in OSA adults.

Multiple brain areas in OSA showed increased R2∗ values before CPAP, indicative of higher iron, over controls and included the amygdala, insula, hippocampus, cerebellum, medulla, and pons nearby areas. The R2∗ values continued to increase in multiple sites at 3-mo CPAP treatment in OSA, and those sites included the cerebellum, thalamus, and cingulate. However, after 9-mo CPAP usage, none of the brain regions showed increased R2∗ values in OSA over baseline.

OSA patients show increased iron content in multiple sites over controls, which progressively increased in several sites, even after 3-mo CPAP use, and started to clear after 9-mo. The findings suggest a means for intervention to lessen brain injury by interfering with iron accumulation in OSA.