The hallmarks of fibromyalgia are widespread muscle and skeletal pain and tenderness at numerous soft tissue sites on the body upon palpation, according to classification criteria promulgated by the American College of Rheumatology (ACR) (Wolfe et al. 1990). The case definition requires both widespread pain (pain on both sides of the body, above and below the waist, and including axial skeletal pain) lasting for at least 3 months and pain (not just tenderness) in at least 11 of 18 tender point sites on palpation with an approximate force of 4 kg. The presence of a second clinical disorder does not exclude a diagnosis of fibromyalgia. Other symptoms of fibromyalgia include fatigue, sleep disturbance, morning stiffness, and cognitive impairment, but those are not sensitive and specific enough to use for classification (Wolfe et al. 1990). Early characterization of the condition as an inflammation of muscle (hence the label fibrositis) have not been borne out through research (Goldenberg 1999). There is no pathologic or laboratory test with which to confirm the diagnosis. And there are no widely accepted causative factors. Fibromyalgia’s prevalence in the general population is about 3.4% in women, and 0.5% in men, so it is one of the more common rheumatologic disorders (Wolfe et al. 1995). Its prevalence increases with age (Wolfe et al. 1995). On the basis of longitudinal studies, the course is chronic but variable in intensity (Wolfe et al. 1997). It should be noted that the existence of fibromyalgia as a distinct disease entity is considered controversial by some expert commentators (Nimnuan et al. 2001; Pearce 2004).
For consideration as a primary study, the basis of diagnosis of fibromyalgia has to include symptom reporting and physical examination, rather than only symptom-based criteria. Fibromyalgia was one of 12 primary health-outcome measures studied by Eisen and colleagues (2005), who conducted medical evaluations in phase III of VA’s nationally representative, population-based study. From 1999- 2001, 1,061 Gulf War veterans and 1,128 non-Gulf War veterans were evaluated. They had been randomly selected from 11,441 deployed and 9,476 nondeployed veterans, who had participated in the phase I questionnaire in 1995 (Kang et al. 2000). Researchers were blinded to deployment status. The diagnosis of fibromyalgia was based on diffuse body pain and pain on physical examination, following the ACR criteria (Wolfe et al. 1990). Self-reported diagnoses of fibrositis or fibromyalgia did not vary between deployed and nondeployed veterans (0.6% and 0.8% respectively; OR 1.21, 95% CI 0.36-4.10, adjusted for age, sex, race, cigarette-smoking, duty type, service branch, and rank). However, fibromyalgia diagnosed on the basis of physical examination was present in 2.0% of deployed and 1.2% of nondeployed veterans (adjusted OR 2.32, 95% CI 1.02- 5.27). Strengths of the study include the population-based sampling strategy, blinding of evaluating physicians, and use of validated diagnostic criteria based on physical examination. Limitations include the potential for substantial selection bias due to modest participation rates of 53% of Gulf War veterans and 39% of non-Gulf War veterans and the deployed veterans being significantly younger, less educated, less likely to be married, and of lower income, although the analysis adjusted for most of those factors.
Smith and colleagues (Smith et al. 2000) performed a study of postwar hospitalizations (1991-1997) among 551,841 deployed and 1,478,704 nondeployed active duty personnel. The