Objective Based on the dynamic changes in electroencephalogram (EEG) signals during the sleep and wakefulness states in athletes with chronic insomnia, this study aimed to analyze the characteristics of central nervous system regulation and provide feasible monitoring methods for the prevention and treatment of chronic insomnia.

Methods Overnight sleep data from 30 elite male athletes (15 with chronic insomnia and 15 with normal sleep patterns) were recorded using polysomnography. EEG characteristics during wakefulness were assessed using a 64-channel EEG system at before sleep and upon waking. Exercise performance was evaluated by 30-second Wingate test.

Results Compared with the normal sleep group, chronic insomnia athletes exhibited prolonged sleep onset latency (SOL) and increased awakening time (AT), with significantly shortened in total sleep time, lower sleep efficiency (SE), and a significantly reduction in proportion of deep sleep time (DST) and rapid eye movement (REM) sleep (P＜0.01). During the sleep initiation stage, the power spectral density of δ and σ bands were increased more slowly, while the β band were decreased significantly more slowly in the chronic insomnia group compared to the normal sleep group (P＜0.05). During the sleep maintenance stage, the DST phase exhibited lower θ and σ bands power, while the REM phase showed higher α band power density (P＜0.001). During the sleep transition stage, the α, σ, and β bands powers were higher (P＜0.001), whereas the δ band power was lower (P＜0.01). Throughout the whole night and in the first 10 minutes of the non-rapid eye movement (NREM) phase, chronic insomnia athletes had fewer sleep spindles (P＜0.01) and lower spindle density (P＜0.01). From the brain source localization results, chronic insomnia athletes exhibited higher δ-band activity in the left prefrontal cortex (e.g., medial frontal gyrus) before sleep (P＜0.05) compared with normal sleep athletes. Regarding brain functional network connectivity, the local efficiency of the δ band before sleep and in the morning, the clustering coefficient of the β band, the global efficiency of the θ and σ bands in the morning, the Laplacian eigenvalue of the β band in the morning, and the Laplacian eigenvalues of the α and β bands before sleep were all lower in the chronic insomnia group compared to the normal sleep group (P＜0.05).

Conclusions In chronic insomnia athletes, the δ-band activity of the left prefrontal cortex (e.g., medial frontal gyrus) is excessively elevated before sleep, leading to decreased brain functional network efficiency and disrupting the wake-sleep transition process. Accordingly, these changes prolonged SOL and increased AT, ultimately reducing SE. Additionally, the slow increase in low-frequency brain waves and the delayed decrease in high-frequency brain waves during sleep may contribute to a reduced proportion of DST and REM sleep, further impairing the functional network connectivity of the brain upon waking.