Obesity, Weight Loss, and Progression of Disability in Rheumatoid Arthritis

Abstract

Objective: Cross-sectional studies have demonstrated that obese patients with rheumatoid arthritis (RA) often report greater disability. The longitudinal effects of obesity, however, are not well-characterized. We evaluated associations between obesity, weight loss, and worsening of disability in patients of 2 large registry studies, which included patients who were followed for longer periods of time.

Methods: This study included patients with RA from the National Data Bank for Rheumatic Diseases (FORWARD) (n = 23,323) and the Veterans Affairs RA (VARA) registry study (n = 1,697). Results of the Health Assessment Questionnaire (HAQ) or Multidimensional HAQ (MD-HAQ) were recorded through follow-up. Significant worsening of disability was defined as an increase of >0.2 in HAQ or MD-HAQ scores. The Cox proportional hazards model was used to evaluate the risk of worsening of disability from baseline and to adjust for demographics, baseline disability, comorbidity, disease duration, and other disease features.

Results: At enrollment, disability scores were higher among severely obese patients compared to those who were overweight both in FORWARD (β = 0.17 [95% confidence interval (95% CI) 0.14, 0.20]; P < 0.001) and in the VARA registry (β = 0.17 [95% CI 0.074, 0.27]; P = 0.001). In multivariable models, patients who were severely obese at enrollment had a greater risk of progressive disability compared to overweight patients in FORWARD (HR 1.25 [95% CI 1.18, 1.33] P < 0.001) and in the VARA registry (HR 1.33 [95% CI 1.07, 1.66]; P = 0.01). Weight loss following enrollment was also associated with a greater risk in both cohorts. In the VARA registry, associations were independent of other clinical factors, including time-varying C-reactive protein and swollen joint count.

Conclusion: Severe obesity is associated with a more rapid progression of disability in RA. Weight loss is also associated with worsening disability, possibly due to it being an indication of chronic illness and the development of age-related or disease-related frailty.

Figure 1

Linear extrapolation of HAQ scores over time stratified by BMI category based on longitudinal regression models in the Forward registry (not shown for VARA). Model adjusted for enrollment age, age*year, sex, race, baseline HAQ, baseline HAQ*year.

Figure 2

Survival without worsening HAQ in Forward (not shown for VARA) by enrollment BMI category (severely obese and overweight) and weight loss from age 30, adjusting for age, sex, and baseline HAQ.