What is the most important factor affecting the cognitive function of obstructive sleep apnea syndrome patients: a single center study

Abstract

Objective Patients with obstructive sleep apnea syndrome (OSAS) usually complain of daytime hypersomnia and decrease in cognitive function, which affects the quality of their work and life. The reason why the cognitive function of OSAS patients decreased remains controversial. The aim of this study is to evaluate the impairment and the main influencing factors of cognitive function in OSAS. Methods There were totally 50 OSAS patients (OSAS group) and 25 volunteers (control group) included in our study. All of them were monitored by polysomnography (PSG) and tested by Continuous Performance Test (CPT), n-back test and Stroop Color-Word Test (CWT) to evaluate their sleep condition and cognitive function. Results No significant difference was found between the two groups in total sleep time and sleep efficiency (P > 0.05, for all). Compared with control group, OSAS group had significant increased time of non-rapid eye movement (NREM) sleep stage Ⅰ and stage Ⅱ, significant decreased time of stage Ⅲ (P < 0.05, for all), while no significant difference in rapid eye movement (REM) sleep. The arousal index (AI) of the OSAS group was significantly higher than control group (P < 0.05). Patients in OSAS group had significantly lower scores in the cognitive function tests (P < 0.01), which showed the ability of attention, response, memory, discernibility and performance were injured. The damage had no significant connection with the severity of the apnea hyponea index (AHI) and hypoxia (P > 0.05, for all), while had significant connection with AI and NREM Ⅲ (P < 0.05, for all). The rate of OSAS patients who underwent nasal continuous positive airway pressure (nCPAP) treatment was very low, only 8% (4/50). Conclusion The abnormality of OSAS patients' sleep structure is characterized with sleep fragmentation and decrease of NREM Ⅲ, which may be the main factors of cognitive impairment. Exploration of treatment methods targeted on regulating the effected hormones and receptors is meaningful.