Associations between hypoxia parameters in obstructive sleep apnea and cognition, cortical thickness, and white matter integrity in middle-aged and older adults.

OBJECTIVE: This study aimed to investigate the association between each parameter of intermittent hypoxia in obstructive sleep apnea (OSA) and the cognitive profile, cortical thickness, and white matter integrity in middle-aged and older adults.
METHODOLOGY: Participants were newly diagnosed with moderate or severe OSA from the King Chulalongkorn Memorial Hospital, Bangkok, Thailand. Respiratory parameters from polysomnography were extracted. Each participant was tested on a battery of neuropsychological tests and underwent an MRI scan of the brain. Cortical thickness analysis and diffusion tensor imaging analysis were performed. Participants were classified as having either severe or mild hypoxia based on parameters of hypoxia, i.e., oxygen desaturation index, lowest oxygen saturation, and the percentage of total sleep time spent below 90% oxygen saturation.
RESULTS: Of 17 patients with OSA, there were 8 men (47%). Median age was 57 years and median AHI was 60.6. Comparison of cortical thickness between the severe and the mild group of each hypoxic parameter revealed two clusters of cortical thinning at the right inferior frontal gyrus (p-value = 0.008) and right inferior parietal gyrus (p-value = 0.006) in the severe desaturation group and a cluster of cortical thinning at the superior parietal gyrus (p-value = 0.008) in the high oxygen desaturation index group. There was no difference in cognitive function or white matter integrity between groups.
CONCLUSIONS: The magnitude of the degree and frequency of desaturations in OSA are associated with a decrease in cortical thickness at the frontal and parietal regions.