Memory and executive dysfunction in patients with severe obstructive sleep apnea and hypopnea syndrome

Abstract

To compare differences in the memory and executive functions between patients with obstructive sleep apnea and hypopnea syndrome (OSAHS) and healthy people. In this study, 50 male Chinese patients with OSAHS were consecutively recruited from the outpatient departments of the Second Xiangya Hospital and 26 healthy individuals were recruited from the physical examination center between October 2013 and March 2014. A full-night polysomnography and a comprehensive neuropsychological assessment were performed on all subjects. The disease severity was scored following the guideline recommended by the American Academy of Sleep Medicine(AASM). Statistical analyses were performed using SPSS 17.0 software for Windows. Compared with the healthy group, OSAHS patients had lower scores on MoCA (28.0 ± 1.1 vs. 22.6 ± 3.0), picture memory (15.7 ± 1.6 vs.11.9 ± 2.7), visual reproduction (12.6 ± 1.2 vs. 9.0 ± 2.2), logical memory (13.7 ± 1.7 vs. 10.9 ± 1.9), digit span forward [8.0(7.8-8.0) vs. 7.0(6.0-8.0)], digit span backward [5(5-6) vs. 4(3-4)], higher continuous wrong numbers on Wisconsin Card Sorting Test (WCST) [7(6-9) vs. 12.4 ± 4.9], lower categories completed [5(4-6) vs. 3.5(2.0-4.3)], longer Stroop Interference time (18.2 ± 9.5 vs. 44.8 ± 13.5); lower correct rate on 2-back test [91.0 ± 2.6 vs. 79(75-81)], longer response time on 2-back test [645 ± 21 vs. 691(653-752)], all with significant differences (P<0.001). (2) In the OSAHS patients, with similar age and education background and BMI, there were positive correlations between scores on MoCA and SaO₂mean (r=0.283, P=0.054), scores on SCWT and Sat90 (r=0.277, P=0.059); but there were negative correlations between scores on MoCA and TSat90 (r=-0.353, P=0.015), visual reproduction (r=-0.308, P=0.035), logical memory (r=-0.306, P=0.036), digit span forward (r=-0.297, P=0.043), backward (r=-0.322, P=0.027) and Sat90. The present study demonstrated that male patients with severe OSAHS had widespread executive dysfunctions (shifting, inhibition, updating) and memory impairments. Nighttime hypoxia and sleep fragmentation were closely related to the cognitive impairments of OSAHS.