AB1069 Chronic widespread pain, sleep problems and pressure pain thresholds in a population sample

Abstract

Background: Chronic musculoskeletal pain is common in the general population and 11% report chronic widespread pain (CWP). A sensitisation of the nociceptive system has been proposed to be one possible mechanism behind CWP, a prerequisite for fibromyalgia (FM). A reduced pressure pain threshold (PPT) has been reported in subjects with FM, but also as an effect of bad sleep. Objectives: The aim was to study pain thresholds in people with CWP in comparison with those having no chronic pain (NCP) or chronic regional pain (CRP), but also in relation to self-reported sleep problems. Methods: From a 21 year follow-up of the Swedish population based Epipain cohort (n 1321), 146 subjects, with and without a report of chronic pain, were invited to a clinical assessment including measurement of PPT. Subjects were classified as having NCP, CRP or CWP, according to the definition of CWP in the ACR 1990 criteria for FM, based on a pain mannequin presenting 0-18 body regions. Sleep problems (initiating sleep, frequent awakenings, not feeling rested, early awakening) were reported by Uppsala Sleep Inventory (four items scored from 1-5, best to worst). PPTs were measured in kPa at eight different anatomical sites representing upper, lower, left and right side of the body using the AlgoMed Computerised Pressure Algometer FPIX (Medoc Ltd. Advanced Medical Systems, Israel). A mean was calculated from all eight points to create a global pressure pain threshold (PPTg), where a lower PPTg indicated a higher sensitivity to pain. ANCOVA regression analysis was performed to study associations between PPTg and reports of chronic pain and sleep problems, controlled for age and gender. Results: Out of 146 subjects, 89 (61%) were women. Mean age was 64.6 (SD 12.7) years. This sub-population from the Epipain cohort reported a high prevalence of CWP without significant difference between men and women (33.9% vs 44.9%; p=0.411). Women had lower PPTg than men (345.0 kPa vs. 563.9 kPa; p<0.001). Subjects classified as CWP had lower PPTg than those classified as NCP (362.0 kPa vs. 479.9 kPa; p=0.003). A report of CRP did not affect PPTg in comparison with those reporting NCP (471.8 kPa vs. 479.9 kPa; p=0.855). The number of reported pain regions correlated negatively with PPTg in women (r=-0.384; p<0.001) but not in men (r=-0.195; p=0.149). Subjects having a score of ≥4 for the sleep problem “frequent awakenings” had lower PPTg than those with a lower score (332.9 vs. 464.7; p<0.001). This was also true, but with less difference, for the sleep problems “not feeling rested” (335.7 vs. 449.1: p=0.023), and “early awakening” (353.0 vs. 452.6; p=0.020), but not for “initiating sleep” (361.5 vs. 436.8: p=0.199). In the ANCOVA analysis both a higher number of painful regions (B=-9.2; p=0.016) and more problems with frequent awakenings (B=-40.1; p=0.003) were associated to a lower PPTg, controlled for age and gender. Conclusions: Subjects with CWP according to self-reported pain distribution were more sensitive to pain pressure than those with CRP and NCP, and so were also subjects reporting problems with sleep. In the clinic, self-report of CWP can be used as an indicator of pain sensitivity, but it is also important to assess sleep problems, and especially frequent awakenings and reports of not feeling rested.