Can the Assessment of the Circadian Rhythm of Pain Be Shortened? A Study of Community-Dwelling Participants with Chronic Pain

Abstract

Purpose: This study aimed to juxtapose the circadian rhythm of pain with the conventional 7-day assessment and ascertain the feasibility of condensing the evaluation of the circadian rhythm of pain into a 3-day timeframe.

Patients and methods: Seventy-three patients with pain persisting for a minimum of 3 months and a numerical rating scale (NRS) score of ≥2 were recruited from three medical centers. The circadian patterns of pain were appraised over a 7-day period by quantifying the intensity of pain at six temporal junctures each day using a 10-cm visual analog scale (VAS). Cluster analysis was performed using six standardized variables derived from the VAS score of each participant at six designated time points to identify cohorts with analogous circadian rhythms of pain. The clusters were discerned for the 7- and 3-day assessments (Tuesday-Thursday, Friday-Sunday, and Sunday-Tuesday), according to the research objectives. Cohen's kappa coefficient was calculated to gauge the intra-observer variability to assess the consistency between the outcomes of the cluster analysis for the 7-day assessment and each of the 3-day assessments.

Results: The highest Cohen's kappa coefficient was observed for the 3-day evaluation spanning from Friday to Sunday, indicating a substantial concordance with the results of the 7-day assessment.

Conclusion: Our results suggest that it may be prudent to consider implementing a condensed 3-day evaluation of the circadian rhythm of pain that is tailored to individual characteristics. This approach will allow a better understanding of the diurnal rhythms of chronic pain in patients and implement more targeted and specific pain management strategies. Furthermore, it will contribute to increased patient satisfaction through early intervention.

Keywords: chronic pain; circadian rhythm; pain; physical activity.

Figure 1

Categorization of the circadian rhythm of pain according to the 7-day assessment. The following criteria are applied to each cluster: CL1: The pain intensity is minimum at the time of awakening, but it increases subsequently and exceeds the Z-score 0 after noon. CL2: The pain intensity is above Z-score 0 at the time of awakening and at 21:00, but below Z-score 0 during the day. CL3: The VAS scores peaks during the waking hours and declined over time. The value is below Z-score 0 post-noon. Each data point is displayed with an error bar.

Figure 2

Categorization of the circadian rhythm of pain according to the 3-day evaluation (Tue–Thu). CL1 and CL3 adhere to the defined criteria, and mirroring clusters are observed during the 7-day assessment. A similar pattern emerges between wakefulness and 21:00 for CL2; however, the rhythmicity surpasses the Z-score threshold at 15:00, leading to its categorization as a separate cluster from the 7-day evaluation clusters. Each data point is displayed with an error bar.

Figure 3

Categorization of the circadian rhythm of pain according to the 3-day evaluation (Fri–Sun). All clusters exhibit an analogous rhythmic pattern similar to that observed during the 7-day evaluation, resulting in their classification as akin clusters. Each data point is displayed with an error bar.

Figure 4

Categorization of the circadian rhythm of pain according to the 3-day evaluation (Sun–Tue). CL1 and CL3 match the 7-day evaluation clusters according to the predefined criteria. In contrast, CL2 does not show a progressive increase over time, with the Z-score falling below 0 at 15:00, despite having a similar awakening VAS value as CL1. As a result, it is classified as a separate cluster unrelated to the 7-day evaluation clusters. Each data point is displayed with an error bar.