Differential associations of hypoxia, sleep fragmentation and depressive symptoms with cognitive dysfunction in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is characterized by recurrent episodes of partial or complete cessation of breathing during sleep and increased effort to breathe. This study examined patients who underwent overnight polysomnographic studies in a major sleep laboratory in Saudi Arabia. The study aimed to determine the extent to which intermittent hypoxia, sleep disruption and depression are independently associated with cognitive impairments in OSA. In the sample of 90 participants, 14 had no OSA, 30 mild OSA, 23 moderate OSA and 23 severe OSA. The findings revealed that hypoxia and sleep fragmentation are independently associated with impairments of sustained attention and reaction time. Sleep fragmentation but not hypoxia, was independently associated with impairments in visuospatial deficits. Depressive symptoms were independently associated with impairments in the domains of sustained attention, reaction time, visuospatial ability, and semantic and episodic autobiographical memories. Since the depressive symptoms are independent of hypoxia and sleep fragmentation, effective reversal of cognitive impairment in OSA may require treatment interventions that target each of these factors.

Keywords: Sustained attention; autobiographical memory; reaction time; visuospatial ability; vitamin D.