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Lifestyle factors may modify the effect of disease activity on radiographic progression in patients with ankylosing spondylitis: a longitudinal analysis
  1. Sofia Ramiro1,2,
  2. Robert Landewé1,3,
  3. Astrid van Tubergen4,5,
  4. Annelies Boonen4,5,
  5. Carmen Stolwijk4,5,
  6. Maxime Dougados6,7,
  7. Filip van den Bosch8 and
  8. Désirée van der Heijde9
  1. 1Department of Clinical Immunology & Rheumatology, Amsterdam Rheumatology Center, University of Amsterdam, Amsterdam, The Netherlands
  2. 2Department of Rheumatology, Hospital Garcia de Orta, Almada, Portugal
  3. 3Department of Rheumatology, Atrium Medical Center, Heerlen, The Netherlands
  4. 4Department of Medicine, Division of Rheumatology, Maastricht University Medical Center, Maastricht, The Netherlands
  5. 5School for Public Health and Primary Care (CAPHRI), University of Maastricht, Maastricht, The Netherlands
  6. 6Department of Rheumatology, Hôpital Cochin, Paris-Descartes University, Paris, France
  7. 7Clinical Epidemiology and Biostatistics, PRES Sorbonne Paris-Cité, Paris, France
  8. 8Department of Rheumatology, University of Ghent, Ghent, Belgium
  9. 9Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
  1. Correspondence to Dr Sofia Ramiro; sofiaramiro{at}


Objectives To investigate the complex relationship between inflammation, mechanical stress and radiographic progression in patients with ankylosing spondylitis (AS), using job type as a proxy for continuous mechanical stress.

Methods Patients from the Outcome in Ankylosing Spondylitis International Study were followed up for 12 years, with 2-yearly assessments. Two readers independently scored the X-rays according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Disease activity was assessed by the AS Disease Activity Score C reactive protein (ASDAS-CRP). The relationship between ASDAS and spinal radiographic progression was investigated with longitudinal analysis, with job type at baseline (physically demanding (‘blue-collar’) versus sedentary (‘white-collar’) labour) as a potential factor influencing this relationship. The effects of smoking status and socioeconomic factors were also investigated.

Results In total, 184 patients were included in the analyses (70% males, 83% human leucocyte antigen-B27 positive, 39% smokers, 48% blue-collar workers (65/136 patients in whom data on job type were available)). The relationship between disease activity and radiographic progression was significantly and independently modified by job type: In ‘blue-collar’ workers versus ‘white-collar’ workers, every additional unit of ASDAS resulted in an increase of 1.2 versus 0.2 mSASSS-units/2-years (p=0.014 for the difference between blue-collar and white-collar workers). In smokers versus non-smokers, every additional unit of ASDAS resulted in an increase of 1.9 versus 0.4 mSASSS-units/2-years.

Conclusions Physically demanding jobs may amplify the potentiating effects of inflammation on bone formation in AS. Smoking and socioeconomic factors most likely confound this relationship and may have separate effects on bone formation.

  • Spondyloarthritis
  • Ankylosing Spondylitis
  • Disease Activity
  • Outcomes research

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