title: Specific and number of comorbidities are associated with increased levels of temporomandibular pain intensity and duration.
abstract: BACKGROUND
  Temporomandibular pain disorder (TMD) is a common pain condition in the face. People with TMD report multiple pain comorbidities. The presence of fibromyalgia and migraine in people with TMD is associated with an increase in TMD pain intensity and duration. However, data on the relationship between increasing number of pain comorbidities and TMD pain are rare. The aims of this study were: firstly to evaluate the extent to which increasing number of comorbidities is associated with increasing TMD pain intensity and duration; and secondly to evaluate the extent to which the presence of specific comorbidities is associated with increasing TMD pain intensity and duration.
  
  
  METHODS
  The sample included 180 people seeking TMD treatment at Boston and Montreal clinics. TMD was diagnosed using the Research Diagnostic Criteria for TMD. A Numerical Pain Rating Scale assessed TMD pain intensity and participants provided their TMD pain duration in a study questionnaire. The comorbidities of migraine, chronic fatigue syndrome, irritable bowel syndrome, interstitial cystitis and restless leg syndrome were diagnosed by 5 validated diagnostic questionnaires. The associations were analyzed by linear regression, controlling for confounders.
  
  
  RESULTS
  There was a positive association between the number of comorbidities present and TMD pain intensity (p < 0.01) and between the number of comorbidities present and TMD pain duration (p < 0.01). Also, the presence of migraine was positively associated with TMD pain intensity (p < 0.01) and the presence of chronic fatigue syndrome was positively associated with TMD pain intensity (p < 0.05) and with TMD pain duration (p < 0.01). When TMD patients were separated into groups, these associations did not change for the myofascial pain group, whereas in the non-myofascial pain group, the relationship between number of comorbidities and TMD pain duration was the only one still present.
  
  
  CONCLUSIONS
  This study shows that the number of comorbidities is positively associated with TMD pain duration and intensity. The presence of specific conditions, such as migraine and chronic fatigue syndrome, is associated with an increase in TMD intensity and duration.
authors.affiliation: Division of Oral Health and Society, Faculty of Dentistry, McGill University, Montreal, QC, H3A 1G1, Canada, haissam.dahan@mail.mcgill.ca.
authors.forename: Haissam
authors.initials: H
authors.lastname: Dahan
authors.forename: Yoram
authors.initials: Y
authors.lastname: Shir
authors.forename: Ana
authors.initials: A
authors.lastname: Velly
authors.forename: Paul
authors.initials: P
authors.lastname: Allison
mesh_terms: D000328:Adult; D018856:Cystitis, Interstitial / Q000150:complications* / Q000175:diagnosis; D015673:Fatigue Syndrome, Chronic / Q000150:complications* / Q000175:diagnosis; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications* / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000150:complications* / Q000175:diagnosis; D012148:Restless Legs Syndrome / Q000150:complications* / Q000175:diagnosis; D012720:Severity of Illness Index; D013001:Somatoform Disorders; D011795:Surveys and Questionnaires; D013706:Temporomandibular Joint Dysfunction Syndrome / Q000150:complications / Q000175:diagnosis*