Association between PTSD symptoms and sigma power during stage 2 sleep in North Korean refugees with traumatic experience

Post-traumatic stress disorder (PTSD) is associated with abnormalities in the sleep electroencephalography (EEG) measured using polysomnography. Sleep spindles, a defining feature of N2 sleep, are partly reflected in sigma-band power, an index associated with sleep-dependent memory processes that may be relevant for PTSD. This study aimed to investigate the associations between PTSD and sleep EEG power among North Korean refugees. This study recruited 23 North Korean refugees with traumatic experiences. All participants completed self-reported questionnaires, including the Impact of Event Scale-Revised (IES-R), and underwent polysomnography (PSG) to record EEG signals during sleep. Power spectral analysis of EEG was conducted across six channels (C3, C4, F3, F4, O1, and O2) in four different sleep stages (N1, N2, N3, and REM). Sigma power during N2 sleep demonstrated significant positive correlations in the IES-R total score across all six channels. Exploratory spindle analyses also showed associations between spindle activity and trauma symptom severity. The current study reveals that N2 sleep sigma power, which represents the sleep spindle, was associated with PTSD symptoms in North Korean refugees. These results indicate sleep spindles as a neurophysiological marker of PTSD symptoms in refugees with traumatic experiences.