Background/aims: To test whether mechanical hyperalgesia is associated with multiple idiopathic pain disorders (IPDs) and whether this relationship is independent of the confounding effects of psychosocial factors. Methods: One hundred eighteen subjects with chronic orofacial pain (COFP) were identified from their questionnaire responses to a population study in North West England. All subjects had a tender point examination according to the American College of Rheumatology classification. Validated tools on the questionnaire were used to identify presence of other IPDs (irritable bowel syndrome and chronic widespread pain) and psychosocial factors (anxiety, depression, health anxiety, sleep disturbance and reporting of somatic symptoms and adverse life events). Results: Of the 118 subjects, 47.6% (n = 56) had COFP, 34.7% (n = 41) had COFP plus one IPD and 17.8% (n = 21) had all three IPDs. Univariate analysis revealed a dose-response relationship between number of tender points (TPs) and number of IPDs [2-6 TPs (OR 2.6, 95% CI 1.0-7.3), ≥7 TPs (OR 10.5, 95% CI 3.8-29.3)] and number of IPDs and psychological distress [anxiety (OR 2.8, 95% CI 1.2-6.4), depression (OR 4.3, 95% CI 1.7-10.6), sleep disturbance (OR 4.8, 95% CI 1.6-14.6)]. The relationship between IPDs and TPs persisted after adjusting for psychosocial factors in multivariate analyses [2-6 TPs (OR 2.5, 95% CI 0.8-7.8) ≥7 TPs (OR 10.7, 95% CI 3.4-33.7)]. Conclusion: The dose-response relationship between TPs and IPDs needs further investigation to determine the temporal nature of these relationships and to disentangle the complex gene-environment relationships that may influence the occurrence of multiple IPDs.
The authors are most grateful to the pain research group at the Arthritis Research Campaign Epidemiology Unit and staff/patients of The Handforth Health Centre and Handforth Clinic for their help with the study.
Vishal Aggarwal also has a part-time appointment as a Senior Lecturer in Academic General Dental Practice at the school of medicine and dentistry, Queen Mary’s University,London and Dr John McBeth has an appointment as a Reader in Epidemiology at Arthritis Research UK Primary Care Centre, University of Keele