The London fibromyalgia epidemiology study: Comparing the demographic and clinical characteristics in 100 random community cases of fibromyalgia versus controls

Objective. To identify demographic and clinical features that distinguish f ibromyalgia (FM) from other chronic widespread pain. Methods. We identified 100 confirmed FM cases, 76 widespread pain controls, and 135 general controls in a random community survey of 3395 noninstituti onalized adults living in London, Ontario. FM cases were distinguished from pain controls using the 1990 American College of Rheumatology (ACR) classi fication criteria for FM. Results. The mean age of FM cases was 47.8 years (range 19 to 86), the same as for pain controls; 86% of FM cases were female versus 67.1% of pain con trols (p < 0.01). FM cases were less educated than general controls (p = 0. 03). Male and female FM cases were similar, except females were older and r eported more major symptoms (both p = 0.02). FM cases reported more severe pain and fatigue, more symptoms, more major symptoms, and worse overall hea lth than pain controls or general controls. The most commonly reported majo r symptoms among FM cases were musculoskeletal pain (77.3%), fatigue (77.3% ), severe fatigue lasting 24 h after minimal activity (77.0%), nonrestorati ve sleep (65.7%), and insomnia (56.0%). Subjects with 11-14 tender points w ere more similar to those with 15-18 tender points than to those with 7-10 points in 11 of 14 clinical variables. On multivariate analysis, 4 symptoms distinguished FM cases from pain controls: pain severity (p = 0.004), seve re fatigue lasting 24 h after minimal activity (p = 0.006), weakness (p = 0 .008), and self-reported swelling of neck glands (p = 0.01). Conclusion. In the general population, adults who meet the ACR definition o f FM appear to have distinct features compared to those with chronic widesp read pain who do not meet criteria.