Compared with control participants, young adults with a long disease duration of juvenile idiopathic arthritis (JIA) may have altered pain perception and sensitivity, according to study results published in Arthritis Research & Therapy. Researchers noted that compared with patients with remitted or active JIA, those with inactive JIA displayed the lowest pain thresholds.
Although previous research has indicated that JIA may alter pain perception, few studies have assessed pain thresholds and sensitivity in these patients.
The current population-based longitudinal study included individuals from central Norway who were diagnosed with JIA between 1997 and 2004. Participants who had a follow-up visit between 2015 and 2017 were included in the analyses. Demographic and clinical features were captured at baseline and reassessed at annual follow-up visits. Patients with JIA were age- and sex-matched with control participants who were identified through the National Population Register of Norway. Patients and control participants underwent a quantitative sensory test (QST), which measures thermal detection and pain thresholds.
To measure cold and warmth detection and pain thresholds, patients held a thermal stimulator and were asked to indicate when they felt the first sensation of cold or warmth. Pressure pain threshold (PPT) was measured using a handheld pressure algometer; participants were instructed to communicate when the sensation of pressure changed into the first sensation of pain. Suprathreshold heat pain response was obtained with continuous stimulation of heat pain on the left forearm. Multilevel models were used to evaluate the relationship between JIA status and pain detection thresholds. Thresholds were also compared between JIA subgroups.
The study cohort included 96 patients with JIA, among whom 71% were women. Median age of patients at QST was 22.7 years and median disease duration was 16.1 years. Among 109 control participants, 71% were women and median age was 23.5 years. Thermal detection and pain thresholds were generally comparable between patients and control participants. Participants with JIA had lower PPTs compared with control participants on both the upper limb (888 vs 1029 kilopascals [kPa], respectively) and lower limb (702 vs 760 kPa, respectively). The minimum temperature needed to evoke pain in the suprathreshold heat pain tests were lower among patients compared with control participants (46 °C vs 47 °C). Self-reported pain was not significantly associated with pain thresholds in any model.
Among the JIA cohort, patients with inactive disease appeared to have higher pain sensitivity compared with patients with active disease. Specifically, patients with inactive disease had lower PPTs (upper limb, 836 kPa; lower limb, 626 kPa) compared with those in remission (893 kPa; 731 kPa, respectively) and those with active disease (910 kPa; 707 kPa, respectively). Cold pain thresholds were also lower in the inactive disease group (upper limb, 16.9 °C; lower limb, 17.4 °C) compared with the remitted (14.3 °C; 11.8 °C, respectively) and active disease (16.2 °C; 13.1 °C, respectively) groups.
In this population-based study, patients with JIA vs control participants had lower pressure pain thresholds. Patients with inactive JIA had the lowest pain threshold.
Study limitations included cohort homogeneity: nearly all patients were White, and all patients were enrolled from Norway. Additional research in a larger cohort may be necessary to better understand pain sensitization in patients with JIA.
“[Our] study indicates…altered pain perception and sensitization after long disease duration of JIA,” the researchers wrote. “A clinical implication of our study may be to emphasize the importance of early intensive treatment to quickly achieve pain-free remission and avoid long-term pain sensitization.”
Arnstad ED, Iversen JM, Uglem M, Glerup M, Romundstad, Sand T, Rugg M. Pain sensitivity in young adults with juvenile idiopathic arthritis: a quantitative sensory testing study. Arthritis Res Ther. 2020;22(1):262.