Obesity Is Common in Axial Spondyloarthritis and Is Associated with Poor Clinical Outcome

Objective To assess the prevalence of overweight and obesity in a large cohort of patients with axial spondyloarthritis (axSpA) in comparison with the general population. To explore the relationship of body mass index (BMI) with clinical outcome in axSpA.

Methods Patients from the Groningen Leeuwarden Axial SpA cohort who visited the outpatient clinic in 2011/2012 were included in this cross-sectional analysis. Body weight, height, disease activity, physical function, and quality of life (QoL) were assessed. Patients were divided into normal weight (BMI < 25 kg/m²), overweight (BMI ≥ 25 to < 30 kg/m²), and obese (BMI ≥ 30 kg/m²). BMI data for the general population in the same demographic region, matched for age and sex, were obtained from the LifeLines Cohort Study.

Results Of the 461 patients with axSpA, 37% were overweight and 22% were obese. In the LifeLines cohort (n = 136,577), 43% were overweight and 15% were obese. Overweight and obese patients were older, had longer symptom duration, and had more comorbidities, especially hypertension. Further, obese patients had significantly higher disease activity, worse physical function, and worse QoL than overweight and normal weight patients (mean Bath Ankylosing Spondylitis Disease Activity Index 4.5, 3.5, 3.8; mean Ankylosing Spondylitis Disease Activity Score 2.8, 2.2, 2.3; median C-reactive protein 5, 3, 3 mg/l; median erythrocyte sedimentation rate 13, 8, 8 mm/h; median Bath Ankylosing Spondylitis Functional Index 5.2, 2.9, 2.9; median Ankylosing Spondylitis QoL Questionnaire 8, 4, 5, respectively). After adjustment for potential confounders, obesity proved to be an independent predictor of worse clinical outcome.

Conclusion In this large observational cohort study, obesity is more common in axSpA than in the general population and it is associated with worse clinical outcome.