Association of obesity with patient-reported outcomes in patients with axial spondyloarthritis: a cross-sectional study in an urban Asian population

To determine if obesity is associated with poorer patient-reported outcomes (PROs) in patients with axial spondyloarthritis (axSpA), we conducted a cross-sectional study using data of the PRESPOND registry from a tertiary referral center in Singapore between 2011 and 2015. Demographics, clinical, and PRO variables were collected. Patients were divided into three categories: normal (BMI < 23 kg/m²), overweight (23 kg/m² ≤ BMI < 27.5 kg/m²) and obese (BMI ≥ 27.5 kg/m²), using Asian BMI classification. The dependent variables are Pain score, Bath Ankylosing Spondylitis Patient Global Score (BAS-G), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Health Assessment Questionnaire (HAQ), and Medical Outcomes Study Short Form 36 version 2 (SF-36). Multivariate regression analyses were performed with these dependent variables and obesity categories, adjusting for confounders. Among 194 patients with axSpA, 32% are overweight while 22% are obese. We found that obese patients had significant poorer pain (β: 11.87, 95%CI 2.13, 21.60) and BAS-G scores (β: 10.18, 95%CI 1.59, 18.76) when compared to normal BMI patients. However, obesity was not associated with BASDAI (β 0.50, 95%CI -0.22, 1.22), BASFI (β 0.08, 95%CI -0.66, 0.81), HAQ (β -0.07, 95%CI -0.21, 0.06), physical component summary (β -0.02, 95%CI -4.47, 4.44), and mental component summary (β -2.85, 95%CI -7.57, 1.88) of SF-36. Obesity was associated with pain score and BAS-G but not with BASDAI, BASFI, HAQ, and SF-36. Further study is needed to examine the causal relationship between obesity and poorer PROs.