Detecting and Characterising Autonomic Dysfunction in Chronic Musculoskeletal Pain: A Cross-Sectional Comparison with Pain-Free Controls

Background/Objectives: Autonomic dysfunction is increasingly being reported in adults with chronic musculoskeletal pain (CMP). We assessed subjective and objective markers of dysautonomia in a CMP population. Methods: We recruited 100 adults with confirmed inflammatory or non-inflammatory musculoskeletal diagnoses associated with CMP attending rheumatology and orthopaedic clinics, and age- and sex-matched 56 pain-free controls. Participants completed the Composite Autonomic Symptom Score 31 (COMPASS-31) dysautonomia scale, Brief Pain Inventory and Hospital Anxiety and Depression Scale, and a 10 min Lean Test (LT). A positive LT was defined as either orthostatic hypotension (OH) or Postural Tachycardia Syndrome (PoTS), determined by standard thresholds for heart-rate and blood-pressure changes as defined in the existing literature. Results: Autonomic symptom burden was identified in 83% of CMP participants at the conventional threshold (COMPASS-31 score ≥ 17) and 72% at the higher threshold (≥28.67) compared with 11% and 0% of controls. Median COMPASS-31 was 41.8 (IQR 25.8–54.8) in CMP and 2.9 (0.4–10.8) in controls (median difference 35.1, 95%CI 29.6–40.4, p < 0.001). A positive Lean Test occurred in 28% of CMP participants (12% PoTS; 16% OH) and 5% of controls (OR 6.80, 95% CI 1.94–36.8, p = 0.001). In the CMP participants, COMPASS-31 discriminated poorly between a positive and negative LT (AUC 0.55, 95%CI 0.42–0.67). No statistically significant difference was detected between inflammatory and non-inflammatory conditions in this sample, on subjective (73% vs. 71%) and objective (27% vs. 29%) assessment. Conclusions: Dysautonomia is common in CMP. The poor discrimination of COMPASS-31 against objective Lean Test findings (AUC 0.55) indicates that subjective and objective measures provide complementary information, supporting consideration of both in autonomic assessment.