To identify demographic and clinical features that distinguish fibromyalgia (FM) from other chronic widespread pain.
We identified 100 confirmed FM cases, 76 widespread pain controls, and 135 general controls in a random community survey of 3395 noninstitutionalized adults living in London, Ontario. FM cases were distinguished from pain controls using the 1990 American College of Rheumatology (ACR) classification criteria for FM.
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 controls (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 reported more major symptoms (both p = 0.02). FM cases reported more severe pain and fatigue, more symptoms, more major symptoms, and worse overall health than pain controls or general controls. The most commonly reported major symptoms among FM cases were musculoskeletal pain (77.3%), fatigue (77.3%), severe fatigue lasting 24 h after minimal activity (77.0%), nonrestorative sleep (65.7%), and insomnia (56.0%). Subjects with 11-14 tender points were 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), severe fatigue lasting 24 h after minimal activity (p = 0.006), weakness (p = 0.008), and self-reported swelling of neck glands (p = 0.01).
In the general population, adults who meet the ACR definition of FM appear to have distinct features compared to those with chronic widespread pain who do not meet criteria.