An observational study of centrally facilitated pain in individuals with chronic low back pain

Introduction: Central pain facilitation can hinder recovery in people with chronic low back pain (CLBP).

Objectives: The objective of this observational study was to investigate whether indices of centrally facilitated pain are associated with pain outcomes in a hospital-based cohort of individuals with CLBP undertaking a pain management programme.

Methods: Participants provided self-report and pain sensitivity data at baseline (n = 97) and again 3 months (n = 87) after a cognitive behavioural therapy-based group intervention including physiotherapy. Indices of centrally facilitated pain were pressure pain detection threshold, temporal summation and conditioned pain modulation at the forearm, Widespread Pain Index (WPI) classified using a body manikin, and a Central Mechanisms Trait (CMT) factor derived from 8 self-reported characteristics of anxiety, depression, neuropathic pain, fatigue, cognitive dysfunction, pain distribution, catastrophizing, and sleep. Pain severity was a composite factor derived from Numerical Rating Scales. Cross-sectional and longitudinal regression models were adjusted for age and sex.

Results: Baseline CMT and WPI each was associated with higher pain severity (CMT: r = 0.50, P < 0.001; WPI: r = 0.21, P = 0.04) at baseline and at 3 months (CMT: r = 0.38, P < 0.001; WPI: r = 0.24, P = 0.02). High baseline CMT remained significantly associated with pain at 3 months after additional adjustment for baseline pain (β = 2.45, P = 0.04, R ² = 0.25, P < 0.0001). Quantitative sensory testing indices of pain hypersensitivity were not significantly associated with pain outcomes at baseline or at 3 months.

Conclusion: Central mechanisms beyond those captured by quantitative sensory testing are associated with poor CLBP outcome and might be targets for improved therapy.