Background/Purpose: No large-scale, national study estimating fibromyalgia (FM) prevalence in the United States (US) has been conducted involving physician evaluation.  The study objective was to provide contemporary data on characteristics and prevalence of FM among a subset of a nationally representative sample of US adults who completed an online subject screener and physician evaluation.

Methods: This multi-stage study included an online subject screener, a site visit for physician evaluation of FM, and an online subject questionnaire.  Subjects were required to be at least 18 years old.  Nationally representative participants were invited to complete the online screener, which included the London Fibromyalgia Epidemiology Study Screening Questionnaire (LFESSQ) to identify those with chronic widespread pain (bilateral, above/below waist for ≥1 week in the past 3 months) (CWP) and sociodemographic questions.  Subjects who screened positive (CWP+) and a control group who screened negative (CWP-) were invited to schedule a site visit at one of 20 sites for physician evaluation of FM including a manual tender point exam until the established cap was met.  CWP+ subjects who were diagnosed with FM based on the physician’s evaluation were designated as having FM and included in prevalence estimates.  Point prevalence estimates of FM were calculated using an adjusted approach for a two-phase study design, and sampling weights reflecting the underlying screened population were used to refine estimates.  Following the site visit subjects completed the subject questionnaire including validated patient-reported outcome instruments to measure FM impact, symptoms, and pain. 

Results: 8,382 (1,939 CWP+, 6,443 CWP-) subjects completed the screener.  A total of 475 subjects attended a site visit: 350 of 1,331 CWP+ and 125 of 502 CWP- who consented to be scheduled for a site visit.  The mean age (years) of the screened sample was 44.1, and there was representation across racial groups with 75.1% white and 12.3% black/African American.  Females were intentionally over-sampled (79.3%) in order to generate precise estimates.  Estimated prevalence (95% CI) of FM was 9.5% (7.2, 11.7) after adjusting for CWP status, gender, age, and race in the screened sample and weighted by 2010 census results for gender to the US population.  Gender-specific prevalence estimates were 12.4% (11.0, 13.8) and 6.8% (4.1, 9.5) among adult women and men, respectively.  The majority (55.0%) of subjects with physician-confirmed FM were obese per WHO criteria (BMI ≥30 kg/m²).  Subjects with physician-confirmed FM had a mean (SD) of 14.4 (3.3) tender points, and 90.1% had ≥11 tender points.

Conclusion: Based on the results of this nationally representative sample, the FM prevalence among US adults was higher than previously estimated by regional prevalence studies.  The higher prevalence estimate may be a function of changing demographic and clinical characteristics of the US population, increased awareness of FM among patients and providers, study design and factors that influenced study participation.  Clinical characteristics of subjects with FM in this study are consistent with the FM clinical profile in the literature.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-population-based-survey-and-physician-assessment-of-the-characteristics-and-prevalence-of-fibromyalgia/