Fibromyalgia, also called fibrositis, is a chronic and variable rheumatic condition characterized by widespread muscle and skeletal tenderness and fatigue. Diagnosis is based on two criteria of the American College of Rheumatology (ACR): a history of widespread pain lasting at least 3 months and the presence of 11 or more of 18 designated tender points on the body. Other nonspecific symptoms of fibromyalgia are sleep disturbance, morning stiffness, and cognitive impairment. The ACR has developed a definition of chronic widespread pain (CWP) as part of the diagnostic criteria for fibromyalgia: CWP is pain reported in the axial skeleton and two contralateral quadrants that persists for 3 months or longer, that is both right and left sides of the body and both above and below the waist. One of the predesignated pain sites is considered a true tender point only if the person feels pain on application of 4 kg of pressure to the site. There are no laboratory tests to diagnose fibromyalgia or CWP, and their etiology is unknown. It has been noted that fibromyalgia cannot be diagnosed without a physical examination (Buskila 2000) and it has been suggested that CWP and fibromyalgia are points on a continuum of chronic pain disorders (Kuzma and Black 2006). Chronic pain, as distinct from CWP, is discussed in the final section of this chapter, “Symptom Reporting.”
Fibromyalgia has a prevalence in the general population of about 2.0%—3.4% in women and 0.5% in men—and its prevalence increases with age (Johnson 1989). As many as 4 million Americans, mostly women, may have fibromyalgia (American Pain Foundation 2007). CWP has been estimated to occur in 5% of patients seen in general internal-medicine practice and up to 20% of rheumatology-clinic patients (Wolfe 1989). In the United Kingdom, 10-11% of the general population reported having symptoms consistent with the ACR definition of CWP (Papageorgiou et al. 2002).
Primary studies of fibromyalgia include a diagnosis based on symptom reporting and physical examination, preferably using ACR criteria. Primary studies of CWP also needed to include a diagnosis based on ACR criteria. Self-reports, even those using pain manikins (a drawing of a person on which areas of pain can be identified), were not considered to be sufficient for a primary study of either condition. The primary studies for fibromyalgia and CWP are summarized in Table 6-11.
The committee identified three primary studies: two of fibromyalgia (Eisen et al. 2005; Smith et al. 2000) and one of CWP (Ang et al. 2006). In 1999-2001, Eisen et al. (2005) reported on the prevalence of 12 medical conditions in 1061 Gulf War-deployed veterans and 1128 nondeployed veterans who were randomly selected from a national cohort of 11,441 deployed and 9476 nondeployed veterans in all service branches. The veterans were part of the National Health Survey of Gulf War Era Veterans and Their Families, whose first phase was a mail and telephone interview conducted in 1995 (Kang et al. 2000b). Researchers were blinded to deployment status, and combat exposure was not assessed. On the basis of self-reports using the SF-36, the prevalence of fibromyalgia in deployed and nondeployed veterans was 0.6% and 0.8%, respectively, for a nonsignificant OR of 1.21 (95% CI 0.36-4.10). However, when fibromyalgia was diagnosed by physical examination following the ACR criteria (Wolfe et al. 1990), the prevalence was 2% in deployed veterans and 1.2% in nondeployed for a significant