Pain characteristics and psychological factors that mediate the association between obesity and outcomes of interdisciplinary pain rehabilitation: a registry-based cohort study

Obesity is a common comorbidity with chronic pain and is closely related to functional and psychological complications of pain, which are also the main outcomes of interdisciplinary pain rehabilitation programmes (IPRP). How obesity influences IPRP outcomes is poorly understood. This study aims to investigate the role of pain characteristics and psychological factors before IPRP as mediators of the association between obesity and IPRP outcomes (i.e. pain intensity and psychological functioning). Sociodemographic variables, pain characteristics and psychological factors were retrieved from the Swedish Quality Registry for Pain Rehabilitation (SQRP). Data at baseline (pre-IPRP) and 1-year follow-up (FU-IPRP) were used in mediation analysis. Of the 872 patients (mean age 45.8 ± 10.5 years, 80.3% female), 232 (26.6%) were obese (body mass index [BMI] ≥ 30 kg/m²). Patients with obesity reported higher pain intensity (<i>p</i> = 0.02), a higher number of pain locations (<i>p</i> &lt; 0.001), and longer pain duration (<i>p</i> = 0.002) compared to non-obese patients. Significant improvements at FU-IPRP were found in pain intensity and psychological functioning for both obese and non-obese groups. Mediation analysis revealed that pain intensity, pain radiation and depressive symptoms at pre-IPRP reduced the improvement of pain intensity at FU-IPRP among the patients with obesity. Depressive symptoms and pain intensity (or pain radiation) also mediated changes in two psychometric outcomes of IPRP (dysfunctional scale and adaptive coper scale). At FU-IPRP, patients with obesity experienced improvements in pain and psychological well-being, which were mediated by pain intensity, pain radiation, and depression. The roles of these mediators need to be specifically addressed when designing a tailored IPRP for pain patients with comorbid obesity. Patients with chronic pain and comorbid obesity had worse pain characteristics than non-obese peers before participating in a pain rehabilitation program.Pain intensity, pain radiation and depression mediated the improvements of rehabilitation for patients with chronic pain and comorbid obesity. Patients with chronic pain and comorbid obesity had worse pain characteristics than non-obese peers before participating in a pain rehabilitation program. Pain intensity, pain radiation and depression mediated the improvements of rehabilitation for patients with chronic pain and comorbid obesity.

肥胖是慢性疼痛常见的共病类型，且与疼痛引发的功能及心理并发症密切相关，而这类并发症亦是跨学科疼痛康复项目（Interdisciplinary Pain Rehabilitation Programmes, IPRP）的核心评估结局。目前学界对肥胖如何影响跨学科疼痛康复项目结局的机制尚不明晰。本研究旨在探究跨学科疼痛康复项目实施前的疼痛特征与心理因素，在肥胖与该项目结局（即疼痛强度与心理功能）的关联中所发挥的中介作用。
本研究从瑞典疼痛康复质量登记库（Swedish Quality Registry for Pain Rehabilitation, SQRP）中提取了社会人口学变量、疼痛特征及心理因素相关数据。本研究采用基线（pre-IPRP）及1年随访（FU-IPRP）阶段的数据开展中介分析。本研究纳入872例患者，平均年龄为45.8±10.5岁，女性占比80.3%；其中232例（26.6%）为肥胖患者，即体质指数（Body Mass Index, BMI）≥30 kg/m²。
与非肥胖患者相比，肥胖患者报告的疼痛强度更高（p=0.02）、疼痛部位更多（p<0.001）且疼痛病程更长（p=0.002）。在1年随访阶段，肥胖组与非肥胖组患者的疼痛强度及心理功能均出现显著改善。
中介分析结果显示，干预前的疼痛强度、疼痛放射范围及抑郁症状，会削弱肥胖患者在1年随访阶段的疼痛强度改善程度。抑郁症状与疼痛强度（或疼痛放射范围）同样对跨学科疼痛康复项目的两项心理测量结局（功能失调量表与适应性应对量表）的变化起到中介作用。
在1年随访阶段，肥胖患者的疼痛状况与心理福祉均得到改善，这一效应受到疼痛强度、疼痛放射范围及抑郁症状的中介调控。在为共病肥胖的疼痛患者定制跨学科疼痛康复方案时，需针对性考量上述中介变量的作用。
参与疼痛康复项目前，伴共病肥胖的慢性疼痛患者的疼痛特征较非肥胖同类患者更差。疼痛强度、疼痛放射范围及抑郁症状，会介导伴共病肥胖的慢性疼痛患者的康复改善效果。参与疼痛康复项目前，伴共病肥胖的慢性疼痛患者的疼痛特征较非肥胖同类患者更差。疼痛强度、疼痛放射范围及抑郁症状，会介导伴共病肥胖的慢性疼痛患者的康复改善效果。