The Impact of Nocturnal Hypoxemia and Daytime Sleepiness on Cognitive Impairment in Patients with Obstructive Sleep Apnea Syndrome

Ma, Eun Ju; Yoon, Byung Nam; Hwang, Hey Ran; Ha, Choong Kun; Choi, Seong Hye; Yun, Chang Ho

Abstract

BACKGROUND: Patients with obstructive sleep apnea syndrome (OSAS) have some deficits in attention and frontal functions. The pathophysiology of the cognitive dysfunction is still controversial. We investigated the cognitive performances of OSAS patients, and the relationship of cognitive functioning and nocturnal respiratory findings and daytime sleepiness.
METHODS
Neuropsychological testing, the Beck Depression Inventory and the Epworth sleepiness scale (ESS) were administered to 35 patients with OSAS and to 31 normal controls.
RESULTS
Compared to the controls, OSAS patients had significant impairment on the Korean mini mental state examination (K-MMSE), semantic and phonemic fluency, the time and number of correct on the Korean Stroop color word test, the Digit cancellation test and delayed response on the Seoul verbal learning test (SVLT). ESS was significantly correlated with K-MMSE, trail making A, the time and number of correct on the Korean Stroop color word test, delayed recall of SVLT and Rey figure test and number of fulfilled categories on the Wisconsin card sorting test in OSAS patients. The Apnea-hypopnea index (AHI) was significantly correlated with the copy of the Rey figure test. Arousal index, total time slept with oxygen saturation below 90% and the lowest oxygen saturation were not correlated with any neuropsychological parameters.
CONCLUSIONS
Patients with OSAS have cognitive impairment concerning attention, executive function and retrieval of memory. The cognitive impairment may be attributed not to nocturnal hypoxemia, but to subjective daytime sleepiness.