Findings of cognitive function and cerebral metabolic alteration in obstructive sleep apnea

Objectives In obstructive sleep apnea (OSA), characterized by chronically fragmented sleep and intermittent hypoxemia, development of cognitive impairments has been issued. In this study, we investigated the alteration of neuropsychological function and changes in cerebral glucose metabolism in patients with OSA.

Methods Eighteen male patients (age: 49.4 ± 6.9 years) affected by moderate-severe OSA (apnea hyponea Index: 57.1 ± 22.4) and 13 male controls (46.0 ± 9.4) were participated. All subjects performed FDG PET and neuropsychological tests evaluating short- and long-term memory, attention, working memory, and executive function. Functional profiles in neuropsychological function test and brain glucose metabolism were compared between the groups, And the correlation between metabolism, neuropsychological function and clinical characteristics in OSA were evaluated.

Results OSA patients did not show significant reduced neuropsychological performances except reaction time of working memory relative to the controls. However, significant hypometabolism in bilateral lateral prefrontal areas and precunes, and right thalamus were found in OSA patients, which areas are known to predominantly affected by sleep deprivation. Additionally, memory retention and error of working memory scores were correlated with glucose metabolism in parahippocampal gyrus.

Conclusions In this study, the significant alteration in the cerebral metabolism despite minimal impairment in neuropsychological test. Metabolic impairment in the brain regions vulnerable to the sleep deprivation can be helpful to understand the functional impairment in patients with sleep apnea