Background Aggressive, early treatment of RA with new therapeutic agents has dramatically improved the management of RA. However, many studies have failed to show greater improvements in function or disability reduction between targeted control vs. less-aggressive care. The prevalence of obesity is increasing dramatically globally, and may be even higher in RA patients.1
Objectives Because obesity is also a risk factor for disability, we evaluated the extent to which excess weight may independently contribute to poorer physical function (PF) in RA.
Methods RA patients enrolled in an observational study at an academic Inflammatory Arthritis Clinic in Baltimore USA completed the patient global, pain VAS, and PROMIS measures assessing PF, pain, fatigue, sleep, and depression. RA clinical indicators were also collected at the visit. Outcomes were compared in obese and non-obese patients using t-tests and chi-square. Multiple regression was used to evaluate the effects of pain, fatigue, and BMI on PF, after controlling for age and disease activity.
Results Participants were mostly female (82%) and white (83%) with mean (SD) age of 55 (13) years; 24% had ≤ high school; RA duration 12 (9). Mean CDAI was 8.1 (8.1). Most were in CDAI remission (n=57; 32%) or LDA (n=64; 36%); 40 (23%) were in MDA and 16 (9%) in HDA. 49 (28%) were classified as normal weight (BMI 18.5–24.9), 46 (26%) were overweight (BMI 25–29.9), and 82 (46%) were obese (BMI≥30). Men had a significantly higher mean BMI than women (33.6 [8.4] vs. 29.5 [7.2], p=0.006).
As compared to non-obese participants, obese participants had a significantly (p<.05) higher CDAI (6.1 [6.9] vs. 10.4 [8.9]; p=.000, respectively) and worse PF, pain, fatigue, sleep, and depression (mean differences -5.0, -4.6, 4.6, 3.8, 2.9, 3.6, and -4.7, respectively). In regression analyses, pain, fatigue, and BMI (but not sleep or depression) were inversely related to PF, after controlling for age and disease activity. In the final model, pain, fatigue and BMI were significantly and inversely related to PF (β=-.39, -.24, and -.153, respectively) after controlling for age and disease activity (F (5, 170) =55.5, p=.000, adjusted r2=.61).
Conclusions Our results suggest that excess weight also contributes to poorer PF in addition to pain and fatigue. As the prevalence of obesity continues to escalate in RA populations, weight loss may be increasingly important to improve not only physical health, disease activity, and response to treatment, but also pain, fatigue, and PF.
Colmegna et al. High rates of obesity and greater associated disability among people with rheumatoid arthritis in Canada. Clin Rheumatol 2016;35(2):457–60.
Acknowledgements Funding: PCORI IP2-PI0000737 and SC14–1402–10818, CIHR 312205.
Disclosure of Interest None declared