The London Fibromyalgia Epidemiology Study: the prevalence of fibromyalgia syndrome in London, Ontario.

OBJECTIVE: To estimate the point prevalence of fibromyalgia syndrome (FM) among noninstitutionalized Canadian adults; and to assess the effect of demographic variables on the odds of having FM.

METHODS: A screening questionnaire was administered via telephone to a random community sample of 3395 noninstitutionalized adults residing in London, Ontario. Individuals screening positive were invited to be examined by a rheumatologist to confirm or exclude FM using the 1990 American College of Rheumatology classification criteria.

RESULTS: One hundred confirmed cases of FM were identified, of whom 86 were women. Mean age among FM cases was 49.2 years among women, 39.3 years among men (p < 0.02). FM affects an estimated 4.9% (95% CI 4.7%, 5.1%) of adult women and 1.6% (1.3%, 1.9%) of adult men in London, for a female to male ratio of roughly 3 to one. In women, prevalence rises steadily with age from < 1% in women aged 18-30 to almost 8% in women 55-64. Thereafter, it declines. The peak prevalence in men also appears to be in middle age (2.5%; 1.1%, 5.7%). FM affects 3.3% (3.2%, 3.4%) of noninstitutionalized adults in London. Female sex, middle age, less education, lower household income, being divorced, and being disabled are associated with increased odds of having FM.

CONCLUSION: FM is a common musculoskeletal disorder among Canadian adults, especially among women and persons of lower socioeconomic status.