Distinct quantitative sensory testing profiles in female with or without chronic low back pain and concurrent insomnia

This case-control study aimed to determine the pain perception characteristics in the four groups of age-matched females using a standardized and validated Quantitative Sensory Testing (QST) protocol. 

A total of 100 female participants (mean age: 34.3±11.4 years) were purposively recruited and categorized into four groups: (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 underwent a clinical interview to ascertain eligibility, completed self-reported questionnaires, and completed QST. The QST profiles consisted 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 corrections for post-hoc analysis. Spearman's correlations (r) were then performed on the entire sample and each group to explore the associations between QST parameters that showed significant between-group differences and psychological measurements.

The CLBP+I group exhibited lower MPT and PPT in both painful and non-painful areas and impaired CPM compared to the Control group (p0.020). Similar findings were found in PPT (p=0.001) at the back and CPM (p=0.029) compared to the CLBP+ group. 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+ groups displayed higher levels of functional disability, maladaptive beliefs, and psychological distress (depression, anxiety, or stress) than the CLBP+ and Control groups (p0.048). The results of the entire sample revealed that lower MPT or PPT were significantly associated with more severe pain intensity, longer pain duration, greater disability levels, or greater impairments in sleep, psychological distress, or pain catastrophizing (r=0.20-0.45). Nevertheless, only a limited number of associations were identified in the separate group analyses.

This study was the first to explore differences in pain perception characteristics among four distinct 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 comorbid states and those with CLBP alone. 

These findings underscore the importance of incorporating sleep assessments routinely in CLBP management. Additionally, impaired CPM implies that treatments aimed at restoring endogenous pain inhibition may benefit individuals with comorbid conditions. Future studies should validate our findings, evaluate the diagnostic and prognostic value of QST, and explore the neurophysiological mechanisms involved.