0142 DECREASED REGIONAL HOMOGENEITY IN THE DEFAULT MODE NETWORK IN PATIENTS WITH OBSTRUCTIVE SLEEP APNEA

Abstract

Obstructive sleep apnea (OSA) subjects show structural brain injury in a set of interacting cortical sites, the ventral medial prefrontal (vMPF), inferior parietal lobule (IPL), and posterior cingulate cortices (PCC). These areas constitute a unique resting-state circuit dubbed the “default mode network” (DMN), involved in thoughtless behavior, self-referential processing, sleep, and mood regulation. However, the relationship between OSA severity and the DMN integrity remains unclear, a concern, since mood disorders are common in OSA. Our aim was to examine DMN and the relationships with apnea-hypopnea index (AHI) using regional homogeneity (ReHo) procedures in OSA. We acquired resting-state functional MRI scans from 67 newly-diagnosed, treatment-naïve OSA (age 48.0 ± 9.2years; AHI, 35.6 ± 23.5 events/hour; 51 male) and 73 healthy controls (age 47.1 ± 9.3years; 56 male) using a 3.0-Tesla scanner, and assessed mood (Beck Depression Inventory II, BDI-II; Beck Anxiety Inventory, BAI) as well as sleep variables (Epworth Sleepiness Scale, ESS; Pittsburgh Sleep Quality Index, PSQI). After standard pre-processing steps, we calculated whole-brain ReHo maps of each subject by evaluating homogeneity similarity between each voxel and nearest neighbours, normalized to a common space. The ReHo maps were compared between groups using ANCOVA, and correlated with AHI using partial correlation procedures within OSA subjects (FDR corrected p<0.05; covariates: age and gender). No significant differences in age or gender appeared between groups. Both sleep (ESS, 9.8 ± 4.9 vs 5.1 ± 3.5; PSQI, 8.8 ± 4.1 vs 3.6 ± 2.4) and mood scores (BDI-II, 8.4 ± 8.1 vs 3.7 ± 4.9; BAI, 9.4 ± 11.0 vs 3.4 ± 4.5) were significantly higher in OSA over control subjects (p<0.01). Significantly reduced ReHo appeared in multiple sites of the DMN, including the vMPF, IPL, and PCC in OSA compared to controls. Lower ReHo in the PCC was associated with higher AHI within OSA subjects (r=-0.526, p<0.001). DMN is compromised in OSA, indicating that this resting-state network may mediate affected mood and sleep issues. The finding of a negative relationship between AHI and regional synchrony of neural activities in the DMN indicates that disease severity can contribute significantly to DMN integrity, and consequently, mood behaviors mediated by that circuitry. This research was funded by the NIH R01 HL113251 and R01NR015038.