Background/Purpose:
Obesity results in a higher risk for the development of rheumatoid arthritis
(RA) but is associated with less radiographic damage. The evidence for the
effect of obesity on disease outcomes and course has not been synthesized but
is important to understand as it may be a modifiable risk factor that impacts RA
progression and response to treatment.

Methods: A Medline
search was performed (to May 2015) using ‘Obesity’ and ‘Body Mass Index’ as MeSH terms, and with relevant terms and
acronyms in the title and abstract search. The results of this search were
combined with a strategy to identify rheumatoid arthritis studies. Articles
were selected for inclusion if they described composite disease activity
measures or states (DAS28, SDAI, CDAI), individual disease activity measures
(tender and swollen joint counts, ESR, CRP, patient global assessment), patient
reported outcomes (pain, HAQ, fatigue, quality of life scales), or mortality
rates, stratified by body mass index (BMI) category or in relationship to BMI
on a continuous scale. Meta-analysis was completed using the generic
inverse-variance approach with random effects models based on the most adjusted
models presented using RevMan version 5.3.

Results: A total of 1,281 records were screened. After
applying inclusion criteria, a total of 24 articles were identified that
reported on a disease activity measure of interest, 3 reported on the
association with obesity and mortality in RA, and 8 articles described
remission by obesity status. Only 6 out of 19 studies reporting on DAS28 found
higher DAS28 scores at baseline for obese patients in comparison to normal
weight subjects, but 6 out of 8 studies found significantly higher scores in
obese subjects during follow-up. Obese patients demonstrated lower odds of
achieving remission (pooled OR 0.57, 95%CI 0.45 to 0.72, Figure 1) and
sustained remission (pooled OR 0.49, 95%CI 0.32 to 0.74). Of the 12 studies
that reported on ESR and CRP, only 3 found an association between BMI and
baseline ESR and none found a significant association for CRP. Obese patients
had a worse baseline HAQ score in 6 out of 14 studies, worse patient global
assessment of health in 5 out of 11 studies, and higher levels of pain in 5 out
of 8 studies. Three studies measured
the total SF-36 Score, or Physical and Mental Component Scores, with obese
patients having worse quality of life. There was not an increased mortality
risk for obese patients (n=3 studies).

Conclusion:
Obesity decreases the odds of achieving remission in RA, and is associated with increased pain, impaired functional
ability, and decreased quality of life. Interventions
to reduce BMI should be
investigated for the ability to improve disease outcomes.

Figure
1. Meta-Analysis of the Effect of Obesity on Remission in Rheumatoid Arthritis
Studies