Changes in inter- and intrahemispheric connectivity in patients with cardiovascular diseases and obstructive sleep apnea

Objective: to analyze the electroencephalographic (EEG) connectivity in patients with cardiovascular diseases and obstructive sleep apnea. Materials and Methods. A total of 133 polysomnograms in cardiology patients were analyzed. The patients were divided into 4 groups depending on the value of the apnea-hypopnea index (AHI). Based on the wavelet bicoherence method, the level of connectivity of the electrical activity in the brain between all pairs of EEG channels for the entire duration of the night sleep was independently calculated from the polysomnograms. Results. The mean value of interhemispheric connectivity decreased significantly with increasing severity of apnea syndrome almost in all frequency bands. The mean values of occipital interhemispheric connectivity exhibited an inversely proportional trend with an increase of AHI in ∆f6 [4.0-8.0 Hz]: 0.472 [0.391; 0.585], 0.439 [0.402; 0.509], 0.418 [0.384; 0.483], 0.395 [0.359; 0.433] (p=0.012). Intrahemispheric connectivity was superior to interhemispheric connectivity both in the left and right hemispheres and demonstrated heterogeneous dynamics. Conclusion. With increasing AHI, interhemispheric connectivity decreased and intrahemispheric connectivity increased selectively. At the same time, in the group of patients with AHI<10 events/h, this pattern was violated, and the level of EEG connectivity corresponded to the most severe grade of apnea.