Background Sleep disturbance is a common problem affecting over 70% of individuals with chronic low back pain (CLBP). Despite a strong correlation between the two parameters, the potential mechanism underlying the role of sleep in CLBP remains unclear. This study aimed to investigate the characteristics of pain perception in female individuals with CLBP versus age-matched controls with or without insomnia.
Methods A total of 100 female participants were recruited, with 25 individuals with CLBP and insomnia (CLBP-I), 25 with CLBP, 25 with insomnia, and 25 healthy individuals. All participants received clinical interviews for eligibility, completed psychological questionnaires, and underwent quantitative sensory testing (QST). The QST profiles consist of cold pain threshold (CPT), heat pain threshold (HPT), mechanical pain threshold (MPT), pressure pain threshold (PPT), temporal summation of mechanical pain (TSP-M), temporal summation of heat pain (TSP-H), and conditioned pain modulation (CPM). Group differences were determined using the Kruskal-Wallis test with Bonferroni-Holm adjusted Mann-Whitney U tests. Spearman's correlations (r) were then performed within entire samples and each group to explore the associations between QST parameters that showed statistically significant differences among the groups and psychological measurements.
Results Our study found that individuals with CLBP-I exhibited lower MPT and PPT in both painful and non-painful areas and impaired CPM compared to healthy controls (p<0.020). Similar findings were found in PPT (p=0.001) at the back and CPM (p=0.029) compared to those with CLBP. However, there were no significant differences in CPT, HPT, TSP-M, and TSP-H among the four groups (p>0.134). Furthermore, the CLBP-I and insomnia group displayed higher levels of functional disability, maladaptive beliefs, or emotional issues (depression, anxiety, or stress) than healthy controls and the CLBP group (p<0.048). The results of association within the entire sample revealed that lower MPT or PPT were associated with severe pain intensity, prolonged pain duration, greater disability levels, or greater impairments in sleep, negative feelings, or pain catastrophizing (r=0.20-0.45). Nevertheless, the separate group analyses had limited associations and distinctive association patterns.
Conclusion This study was the first attempt to investigate the characteristics of pain perception among four well-characterized groups of individuals with or without CLBP or insomnia. Our results revealed significant differences in pain thresholds, descending inhibitory effects, and psychological status between individuals with CLBP-I and those with CLBP. These findings underscore the importance of incorporating sleep assessments as a routine practice in CLBP. Furthermore, impaired CPM and no differences in TSP may indicate that comorbid conditions predominantly impact antinociceptive mechanisms rather than pronociceptive mechanisms. This implies that the treatments to restore endogenous pain inhibition may benefit individuals with comorbid states. Future studies are warranted to validate our findings, establish the diagnostic and prognostic value of QST, and probe the neurophysiological mechanisms in this population.