Abstract
Impaired spontaneous regional activity and altered topology of the brain network have been observed in obstructive sleep apnea (OSA). However, the mechanisms of disrupted functional connectivity (FC) and topological reorganization of the default mode network (DMN) in patients with OSA remain largely unknown. We explored whether the FC is altered within the DMN and examined topological changes occur in the DMN in patients with OSA using a graph theory analysis of resting-state functional magnetic resonance imaging data and evaluated the relationship between neuroimaging measures and clinical variables. Resting-state data were obtained from 46 male patients with untreated severe OSA and 46 male good sleepers (GSs). We specifically selected 20 DMN subregions to construct the DMN architecture. The disrupted FC and topological properties of the DMN in patients with OSA were characterized using graph theory. The OSA group showed significantly decreased FC of the anterior–posterior DMN and within the posterior DMN, and also showed increased FC within the DMN. The DMN exhibited small-world topology in both OSA and GS groups. Compared to GSs, patients with OSA showed a decreased clustering coefficient (Cp) and local efficiency, and decreased nodal centralities in the left posterior cingulate cortex and dorsal medial prefrontal cortex, and increased nodal centralities in the ventral medial prefrontal cortex and the right parahippocampal cortex. Finally, the abnormal DMN FC was significantly related to Cp, path length, global efficiency, and Montreal cognitive assessment score. OSA showed disrupted FC within the DMN, which may have contributed to the observed topological reorganization. These findings may provide further evidence of cognitive deficits in patients with OSA.
Highlights
Obstructive sleep apnea (OSA) is a common sleep-disordered breathing condition characterized by repetitive cessations of breathing and/or reduced airflow due to frequent episodes of complete or partial obstruction of the upper airway during sleep
Definition of default mode network (DMN) Subregions According to a previous study, we focused on the DMN and chose a specific set of 20 regions of interest (ROI) with substantial agreement with the functional and anatomic partitions of the DMN (Table 1) [16]
The present study applied graph theory approaches to provide evidence that the cognitive impairments observed in patients with obstructive sleep apnea (OSA) might be attributed to the topological configuration of the DMN, which probably resulted from the abnormal DMN functional connectivity (FC)
Summary
Obstructive sleep apnea (OSA) is a common sleep-disordered breathing condition characterized by repetitive cessations of breathing and/or reduced airflow due to frequent episodes of complete (apnea) or partial (hypopneas) obstruction of the upper airway during sleep. These respiratory events lead to sleep fragmentation [1], chronic intermittent hypoxemia [2], repetitive arousals, oxygen desaturation, and hypercapnic hypoxia. OSA is associated with an increased risk of both traffic and occupational accidents [4], decreased quality of life, and long-term health problems resulting from a number of concomitant diseases, including hypertension, cardiovascular impairment, stroke, chronic kidney disease [5], depression [6], anxiety, metabolic syndrome, insomnia, cognitive dysfunction, and even Alzheimer’s disease [7]. The neurological basis of neurocognitive dysfunction in patients with OSA has not been examined in detail
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