In rheumatoid arthritis, country of residence has an important influence on fatigue: results from the multinational COMORA study

Rheumatology (Oxford). 2016 Apr;55(4):735-44. doi: 10.1093/rheumatology/kev395. Epub 2015 Dec 18.


Objectives: To investigate the relationship between country of residence and fatigue in RA, and to explore which country characteristics are related to fatigue.

Methods: Data from the multinational COMORA study were analysed. Contribution of country of residence to level of fatigue [0-10 on visual analogue scale (VAS)] and presence of severe fatigue (VAS ⩾ 5) was explored in multivariable linear or logistic regression models including first socio-demographics and objective disease outcomes (M1), and then also subjective outcomes (M2). Next, country of residence was replaced by country characteristics: gross domestic product (GDP), human development index (HDI), latitude (as indicator of climate), language and income inequality index (gini-index). Model fit (R(2)) for linear models was compared.

Results: A total of 3920 patients from 17 countries were included, mean age 56 years (s.d. 13), 82% females. Mean fatigue across countries ranged from 1.86 (s.d. 2.46) to 4.99 (s.d. 2.64) and proportion of severe fatigue from 14% (Venezuela) to 65% (Egypt). Objective disease outcomes did not explain much of the variation in fatigue ([Formula: see text] = 0.12), while subjective outcomes had a strong negative impact and partly explained the variation in fatigue ([Formula: see text]= 0.27). Country of residence had a significant additional effect (increasing model fit to [Formula: see text] = 0.20 and [Formula: see text] = 0.36, respectively). Remarkably, higher GDP and better HDI were associated with higher fatigue, and explained a large part of the country effect. Logistic regression confirmed the limited contribution of objective outcomes and the relevant contribution of country of residence.

Conclusion: Country of residence has an important influence on fatigue. Paradoxically, patients from wealthier countries had higher fatigue.

Keywords: COMORA; cultural aspects; disease activity; fatigue; inequalities; multinational study; rheumatoid arthritis.

Publication types

  • Multicenter Study
  • Observational Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Arthritis, Rheumatoid / complications*
  • Arthritis, Rheumatoid / epidemiology
  • Cross-Sectional Studies
  • Fatigue / epidemiology
  • Fatigue / etiology*
  • Female
  • Gross Domestic Product / statistics & numerical data
  • Humans
  • Male
  • Middle Aged
  • Residence Characteristics
  • Severity of Illness Index
  • Socioeconomic Factors
  • Young Adult