Sleep Disturbances in Patients with Complex Regional Pain Syndrome: A Pilot Exploratory Study on Pain Characteristics, Functional Impairment, and Psychological Factors

Background/Objectives: Our aim was to evaluate sleep quality and excessive daytime sleepiness in complex regional pain syndrome (CRPS) and explore their associations with pain characteristics, functional impairment, depressive symptoms, and pain coping strategies. Methods: This pilot exploratory, cross-sectional observational study was conducted at a single tertiary rehabilitation center using a convenience sample of 21 adults with CRPS Type I (n = 17) or Type II (n = 4). Sleep quality and daytime sleepiness were evaluated using the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS). Pain was assessed with the Numeric Rating Scale (NRS), Short-Form McGill Pain Questionnaire (SF-MPQ), and PainDETECT Questionnaire (PDQ). Limb-specific disability was measured using the Disability of the Arm, Shoulder and Hand (DASH) questionnaire for upper-extremity CRPS (n = 10) and the Lower Extremity Functional Scale (LEFS) for lower-extremity CRPS (n = 11). Psychological factors and central sensitization were assessed via BDI-II, CSQ, and CSI. Results: Poor sleep quality (PSQI > 5) occurred in 81.0% (17/21) of participants (mean PSQI: 10.1 ± 4.1). ESS-defined excessive daytime sleepiness was identified in 47.6% (10/21) of patients (mean ESS: 9.6 ± 5.8). In unadjusted bivariate correlation analyses of the full cohort (n = 21), global PSQI score significantly correlated with NRS pain intensity (ρ = 0.445, p = 0.0431), SF-MPQ sensory pain (ρ = 0.468, p = 0.0325), SF-MPQ affective pain (ρ = 0.461, p = 0.0354), and SF-MPQ total score (ρ = 0.504, p = 0.0199. Conclusions: Sleep disturbances and excessive daytime sleepiness are highly prevalent in CRPS patients in tertiary care. Exploratory unadjusted analyses link sleep quality with pain severity, particularly sensory and affective dimensions. Given the exploratory design and small subgroup sample sizes, larger prospective studies are needed to confirm these findings.