title: Prevalence of fibromyalgia in a low socioeconomic status population.
abstract: BACKGROUND
  The aim of this study was to estimate the prevalence of fibromyalgia, as well as to assess the major symptoms of this syndrome in an adult, low socioeconomic status population assisted by the primary health care system in a city in Brazil.
  
  
  METHODS
  We cross-sectionally sampled individuals assisted by the public primary health care system (n = 768, 35-60 years old). Participants were interviewed by phone and screened about pain. They were then invited to be clinically assessed (304 accepted). Pain was estimated using a Visual Analogue Scale (VAS). Fibromyalgia was assessed using the Fibromyalgia Impact Questionnaire (FIQ), as well as screening for tender points using dolorimetry. Statistical analyses included Bayesian Statistics and the Kruskal-Wallis Anova test (significance level = 5%).
  
  
  RESULTS
  From the phone-interview screening, we divided participants (n = 768) in three groups: No Pain (NP) (n = 185); Regional Pain (RP) (n = 388) and Widespread Pain (WP) (n = 106). Among those participating in the clinical assessments, (304 subjects), the prevalence of fibromyalgia was 4.4% (95% confidence interval [2.6%; 6.3%]). Symptoms of pain (VAS and FIQ), feeling well, job ability, fatigue, morning tiredness, stiffness, anxiety and depression were statically different among the groups. In multivariate analyses we found that individuals with FM and WP had significantly higher impairment than those with RP and NP. FM and WP were similarly disabling. Similarly, RP was no significantly different than NP.
  
  
  CONCLUSIONS
  Fibromyalgia is prevalent in the low socioeconomic status population assisted by the public primary health care system. Prevalence was similar to other studies (4.4%) in a more diverse socioeconomic population. Individuals with FM and WP have significant impact in their well being.
authors.affiliation: Experimental Physiopathology Post Graduating Program, School of Medicine, University of São Paulo, São Paulo, Brazil. anassumpcao@usp.br
authors.forename: Ana
authors.initials: A
authors.lastname: Assumpção
authors.forename: Alane B
authors.initials: AB
authors.lastname: Cavalcante
authors.forename: Cristina E
authors.initials: CE
authors.lastname: Capela
authors.forename: Juliana F
authors.initials: JF
authors.lastname: Sauer
authors.forename: Suellen D
authors.initials: SD
authors.lastname: Chalot
authors.forename: Carlos A B
authors.initials: CA
authors.lastname: Pereira
authors.forename: Amélia P
authors.initials: AP
authors.lastname: Marques
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003906:Developing Countries / Q000191:economics / Q000706:statistics & numerical data; D004185:Disability Evaluation; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D006304:Health Status; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D019964:Mood Disorders / Q000175:diagnosis / Q000453:epidemiology; D010147:Pain Measurement / Q000379:methods*; D011204:Poverty Areas; D015995:Prevalence; D011787:Quality of Health Care / Q000706:statistics & numerical data; D012923:Social Class; D011795:Surveys and Questionnaires; D014938:Work Capacity Evaluation