title: The association of fatigue, comorbidity burden, disease activity, disability and gross domestic product in patients with rheumatoid arthritis. Results from 34 countries participating in the Quest-RA program.
abstract: OBJECTIVE
  The aim is to assess the prevalence of comorbidities and to further analyse to which degree fatigue can be explained by comorbidity burden, disease activity, disability and gross domestic product (GDP) in patients with rheumatoid arthritis (RA).
  
  
  METHODS
  Nine thousands eight hundred seventy-four patients from 34 countries, 16 with high GDP (>24.000 US dollars [USD] per capita) and 18 low-GDP countries (<24.000 USD) participated in the Quantitative Standard monitoring of Patients with RA (QUEST-RA) study. The prevalence of 31 comorbid conditions, fatigue (0-10 cm visual analogue scale [VAS] [10=worst]), disease activity in 28 joints (DAS28), and physical disability (Health Assessment Questionnaire score [HAQ]) were assessed. Univariate and multivariate linear regression analyses were performed to assess the association between fatigue and comorbidities, disease activity, disability and GDP.
  
  
  RESULTS
  Overall, patients reported a median of 2 comorbid conditions of which hypertension (31.5%), osteoporosis (17.6%), osteoarthritis (15.5%) and hyperlipidaemia (14.2%) were the most prevalent. The majority of comorbidities were more common in high-GDP countries. The median fatigue score was 4.4 (4.8 in low-GDP countries and 3.8 in high-GDP countries, p<0.001). In low-GDP countries 25.4% of the patients had a high level of fatigue (>6.6) compared with 23.0% in high-GDP countries (p<0.001). In univariate analysis, fatigue increased with increasing number of comorbidities, disease activity and disability in both high- and low-GDP countries. In multivariate analysis of all countries, these 3 variables explained 29.4% of the variability, whereas GDP was not significant.
  
  
  CONCLUSIONS
  Fatigue is a widespread problem associated with high comorbidity burden, disease activity and disability regardless of GDP.
authors.affiliation: Copenhagen University Hospital at Glostrup, Department of Rheumatology RM, Nordre Ringvej 57, DK-2600 Glostrup, Denmark. kathrine.l.groen@gmail.com.
authors.forename: Kathrine Lederballe
authors.initials: KL
authors.lastname: Grøn
authors.forename: Lykke Midtbøll
authors.initials: LM
authors.lastname: Ornbjerg
authors.forename: Merete Lund
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authors.lastname: Hetland
authors.forename: Fawad
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authors.lastname: Aslam
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authors.lastname: Aggarwal
authors.forename: Hisahi
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authors.lastname: Yamanaka
authors.forename: Humeira
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authors.lastname: Badsha
authors.forename: Laure
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authors.forename: Maurizio
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authors.lastname: Cutolo
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Ferraccioli
authors.forename: Elisa
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authors.lastname: Gremese
authors.forename: Eun
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authors.lastname: Bong Lee
authors.forename: Nevsun
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authors.lastname: Inanc
authors.forename: Haner
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authors.lastname: Direskeneli
authors.forename: Peter
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authors.lastname: Taylor
authors.forename: Margriet
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authors.lastname: Huisman
authors.forename: Rieke
authors.initials: R
authors.lastname: Alten
authors.forename: Christoph
authors.initials: C
authors.lastname: Pohl
authors.forename: Omondi
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authors.lastname: Oyoo
authors.forename: Sigita
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authors.lastname: Stropuviene
authors.forename: Alexandrosos A
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authors.lastname: Drosos
authors.forename: Eduardo
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authors.lastname: Kerzberg
authors.forename: Codorina
authors.initials: C
authors.lastname: Ancuta
authors.forename: Ayman
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authors.lastname: Mofti
authors.forename: Martin
authors.initials: M
authors.lastname: Bergman
authors.forename: Jaqueline
authors.initials: J
authors.lastname: Detert
authors.forename: Zaraa I
authors.initials: ZI
authors.lastname: Selim
authors.forename: Essam A
authors.initials: EA
authors.lastname: Abda
authors.forename: Blerta
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authors.lastname: Rexhepi
authors.forename: Tuulikki
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authors.lastname: Sokka
mesh_terms: D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000191:economics / Q000453:epidemiology*; D016009:Chi-Square Distribution; D015897:Comorbidity; D017281:Cost of Illness; D004185:Disability Evaluation; D005221:Fatigue / Q000175:diagnosis / Q000191:economics / Q000453:epidemiology*; D005260:Female; D059066:Gross Domestic Product; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D015995:Prevalence; D012307:Risk Factors; D012720:Severity of Illness Index; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires