Researchers at Brigham and Women’s Hospital (BWH) investigated the association between disease activity, sleep, psychiatric distress and pain sensitivity in RA and showed that inflammation is associated with heightened pain sensitivity at joint sites, whereas increased sleep problems are associated with heightened pain sensitivity at both joint and non-joint sites. These findings appear online in BioMed Central’s open access journal, Arthritis Research & Therapy on October 29, 2009.
Researchers from the Division of Rheumatology and Pain Management Center of BWH, and the Chronic Pain and Fatigue Center of the University of Michigan Medical School, assessed experimental pain sensitivity, disease activity, sleep problems and psychiatric distress in 59 women with RA. The researchers used questionnaires to assess the women’s sleep problems and psychiatric distress and measured the levels of C-reactive protein as an indicator of disease activity. Pain sensitivity was measured with pressure pain threshold testing at joint and non-joint sites, with lower pain thresholds indicative of higher pain sensitivity.
The researchers found that sleep problems lowered the pain threshold at all sites, suggesting a defect in central pain processing. This finding emphasises the need for research into the mechanisms underlying sleep disorders and pain in RA patients, particularly given the common occurrence of sleeping problems among RA patients. This autoimmune disease, causing chronic inflammation, affects nearly 1% of the population and sufferers often report ongoing pain in spite of successful anti-inflammatory treatment.
“Since differences in pain sensitivity may shape the course of pain complaints and influence treatment decisions, it is important to understand the factors associated with enhanced pain sensitivity”, lead author Yvonne Lee says, adding, “Physicians and researchers should consider both inflammatory and non-inflammatory factors when evaluating pain in research settings and in the clinic.”