Correlation between cognitive function and hippocampal atrophy and cerebral white matter lesions in patients with obstructive sleep apnea hypopnea syndrome

Abstract

To explore the relationship between cognitive impairment and the changes of hippocampal structure and cerebral white matter on brain magnetic resonance imaging (MRI) in subjects with obstructive sleep apnea hypopnea (OSAHS). A total of 81 snoring patients were monitored by overnight polysomnography (PSG) at Sleep Center, Second Affiliated Hospital, Soochow University from March 2012 to August 2013. Based on the results of apnea-hypopnea index (AHI), they were divided into mild (n = 23), moderate (n = 18), severe OSAHS (n = 23) and primary snoring (n = 17) groups. Periventricular hyperintensity (PVH) related to the severity of cerebral white matter lesions and hippocampal atrophy on brain MRI were evaluated according to the Fukudas method and Scheltens standard. The sequences of regular and perpendicular to bilateral hippocampal fluid attenuated inversion recovery (FIAIR) were used. Montreal cognitive assessment (MoCA) and mini-mental state examination (MMSE) were performed to evaluate the changes of cognitive function in all subjects. The cognitive function scores, especially MoCA, progressively decreased and the scores of hippocampal atrophy and PVH increased as the severity of OSAHS aggravated among these groups. Compared to primary snoring group, MoCA and MMSE scores decreased (24.5 ± 2.7 vs 28.0 ± 1.9, P = 0.000; 27.5 ± 1.4 vs 28.7 ± 1.3, P = 0.013) and hippocampal atrophy and PVH scores increased (2.4 ± 1.2 vs 1.5 ± 1.2, P = 0.007; 3.6 ± 1.0 vs 1.6 ± 1.5, P = 0.000) in the severe OSAHS group. The evaluations of MoCA subdomains further revealed selective reduction in visual space, execution function and delayed memory. PVH scores and hippocampal atrophy scores were negatively correlated with MoCA scores (r = -0.30, P = 0.010; r = -0.30, P = 0.006). Multiple linear regression analysis indicated that the degrees of AHI and hippocampal atrophy were the major risk factors for MoCA scores (standardized regression coefficient: -0.386, -0.247; P = 0.000, 0.020). The scores of hippocampal atrophy and PVH were positively correlated with AHI, oxygen reduction index (ODI) and respiratory related arousal index (RI) and negatively with minimum oxygen saturation (LSaO2) and average oxygen saturation (MSaO2) (P < 0.05). The changes of MRI in hippocampus and cerebral white matter are closely related with cognitive dysfunction. And it may become an objective indicator of assessing cognitive function in OSAHS patients.