Background & Aims
Chronic low back pain (CLBP) is the leading cause of years lived with disability worldwide [1]. Sleep disturbance, particularly insomnia, is a prevalent condition that affects over 70% of individuals with CLBP [2, 3]. While prior studies suggested that sleep disturbance had detrimental effects on peripheral and central sensitization in individuals with or without chronic pain, they provided limited information about the underlying neurophysiological mechanisms [4]. Although prior studies have employed resting-sate electroencephalography (EEG) to investigate the neurophysiological mechanisms of chronic pain [5] or insomnia separately [6]. However, their results are considerably heterogeneous, and no studies have examined resting EEG in individuals with comorbid conditions. Therefore, the current case-control study aimed to characterize spontaneous resting brain activity among four groups of age-matched females, including those with or without CLBP, insomnia, and concomitant conditions.
Methods
One hundred female participants were enrolled and categorized into four subgroups: (1) CLBP and insomnia (CLBP+I, n = 25); (2) CLBP alone (CLBP+, n = 25); (3) insomnia alone (Insomnia+, n = 25); and (4) controls without CLBP nor insomnia (Controls, n = 25). All participants completed clinical questionnaires and five-minute resting-state EEG recordings with eyes closed. Preprocessing and extracting physiologically meaningful brain function features were conducted using DISCOVER-EEG automatically [7]. Analyzed brain features involved global absolute and relative power and global graph measures of functional connectivity. Group differences were examined using one-way analysis of variance (ANOVA) with false discovery rate (FDR) correction. Spearman correlation analyses were performed to examine the associations between various clinical variables and EEG measures. The significance level was set at 0.05.
Results
There were no significant differences in the global absolute power spectral across the four groups, whereas significant between-group differences were observed in global relative delta, theta, and alpha bands. Post-hoc analyses with FDR correction revealed that CLBP+I exhibited significantly higher delta and theta bands, but lower alpha bands than CLBP+, Insomnia+, or Controls. Our results also revealed between-group differences in amplitude-based connectivity for the global cluster coefficient and small worldness in the beta band. Post analyses indicated that compared to Controls, CLBP+I showed significantly increased global cluster coefficient and small worldness in the beta band. The correlation analysis found positive correlations between global relative delta and theta bands with pain intensity, pain duration, or functional disability. Furthermore, small worldness in the beta band activity was positively correlated to insomnia severity, sleep quality, or emotional distress.
Conclusions
This is the first empirical study to characterize oscillatory brain activity and functional connectivity among four well-characterized groups of females with or without CLBP or insomnia. Our findings, which showed increased delta and theta but decreased alpha bands, align with the thalamocortical dysrhythmia model in chronic pain [8-10] and the hyperarousal model in insomnia [6, 11, 12]. Furthermore, the comorbid states showed increased information processing in the beta band, potentially reflecting a compensatory adaptation to information overload from both pain and insomnia. Future research should determine whether these unique neurophysiological biomarkers are pertinent to the comorbid condition. This can help monitor the severity of the comorbid condition and predict treatment response in such cases.
References
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Presenting Author
Jeremy Chang
Poster Authors
Jeremy Chang
MSc
The Hong Kong Polytechnic University
Lead Author
Eliza Sun PhD
The Hong Kong Polytechnic University
Lead Author
Shirley Li PhD
The University of Hong Kong
Lead Author
Qijing Liu MSc
The Hong Kong Polytechnic University
Lead Author
Ping Liang MSc
Lead Author
Dino Samartzis DSc
Rush University Medical Centre
Lead Author
Siu Ngor Fu PhD
The Hong Kong Polytechnic University
Lead Author
Arnold YL Wong
The Hong Kong Polytechnic University
Lead Author
Topics
- Lifestyle Issues: Sleep/Diet/Exercise/Social Interactions