Resting-State Brain FMRI Study Of Frequency Dependent Changes In Patients With Obstructive Sleep Apnea

Objective:Previous studies in our group have shown that there is low-frequency spontaneous brain activity in the brain of patients with obstructive sleep apnea（OSA）,which is closely related to their cognitive impairment.However,it is unclear if low-frequency spontaneous brain activity is related to specific frequency bands in OSA patients.In this study,amplitude of low-frequency fluctuation（ALFF）method was used to explore the characteristics of spontaneous brain activity in classical frequency band（0.01-0.1 Hz）and five specific frequency bands（slow-2 to slow-6）in patients with OSA,and to analyze the relationship between spontaneous brain activity and clinical evaluation.Methods:A total of 52 men with newly-diagnosed moderate to severe OSA and 62 healthy controls（HCs）matched to sex and age were collected in the First Affiliated Hospital of Nanchang University from July 2017 to March 2022.At the same time,the resting magnetic resonance image data of each subject were collected and the clinical scale was evaluated.Using DPABI and SPM12 based on MATLAB R2018a to calculate the ALFF values of the classical frequency band and five specific frequency bands,calculating the difference of brain regions between groups according to the two-sample t-test.In this study,the method of analysis of variance（NOVA）was used to investigate the interaction of voxel whole brain ALFF between groups（OSA group vs HCs group）and frequency band（GRF correction,voxel level P<0.01,cluster level P<0.05）.Based on the interaction,a post-t test was used to compare the differences of different frequency bands between groups（Bonferroni correction（4 clusters×5 bands）,P<0.0025（0.05/20））.Pearson correlation analysis was used to assess the association of ALFF changes with clinical data（P<0.05）.This study has been approved by the Hospital Research Ethics Committee.Results:（1）Compared with the HCs group,the ALFF values were significantly decreased in OSA patients in the following areas:the bilateral precuneus/posterior cingulate cortex in the classical frequency band and slow-2～slow-5 band;the left inferior parietal lobule and bilateral angular gyrus in the classical frequency and the slow-4 band;the brainstem in the slow-2 band and the slow-3 band;the right fusiform gyrus in the slow-3 band;and the left middle frontal gyrus in the classical band（GRF correction,voxel level P<0.01,cluster level P<0.05）.The ALFF values were significantly increased in OSA patients in the following areas:the right cerebellum posterior lobe of the classical frequency band,slow-2 band and slow-5 band;the left cerebellum posterior lobe in the classical frequency band,slow-3 band,slow-4 band and slow-6 band;the left fusiform gyrus of the classical frequency band,slow-4 band and slow-5 band;the left superior frontal gyrus of classical frequency band and slow-2～slow-4 band;the left inferior frontal gyrus of classical frequency band and slow-4～slow-6 band（GRF correction,voxel level P<0.01,cluster level P<0.05）.ANOVA analysis showed the interaction of intergroup and band interactions in the bilateral inferior parietal lobule,bilateral precuneus/posterior cingulate cortex,left angular gyrus.（2）The results of Pearson correlation analysis between ALFF values of multiple abnormal brain regions and clinical data in patients with OSA were as follows:bilateral precuneus/posterior cingulate cortex was positively correlated with minimum oxygen saturation（Sa O₂）and average Sa O₂in classical frequency band and slow-2～slow-5,and negatively correlated with microarousal index;it was negatively correlated with apnea hypopnea index in classical band,slow-2 band and slow-5 band;it was positively correlated with naming in classical frequency band and slow-4.The left inferior parietal lobule was positively correlated with naming in classical band and slow-4 band;it was positively correlated with N3 in classical band,and negatively correlated with delayed recall in classical band and slow-4 band.The left angular gyrus was positively correlated with the minimum Sa O₂and naming in classical frequency band and slow-4,and negatively correlated with sleep efficiency;and positively correlated with abstraction in classical band;and negative correlation with snoring history in slow-4.The right angular gyrus in the slow-4 band was negatively correlated with snoring history and microarousal index（P<0.05）.Conclusion:（1）The results of this study showed that there were frequency-specific differences in spontaneous brain activity in OSA patients,mainly manifested in abnormal activity in most brain regions of the default network and showed frequency dependence.（2）The differential brain area in OSA patients was related to clinical indicators such as cognition.This study identified frequency-band characteristics related to brain damage,expanded the cognitive neuroimaging mechanism,and provided additional OSA neuroimaging markers.