Background/Purpose

Increased adiposity is associated with increased production of pro-inflammatory adipokines and raised inflammatory markers. As a result, standard disease activity scores (DAS) may be greater in obese rheumatoid arthritis (RA) patients, with important implications for their treatment in modern target based regimens. There is limited longitudinal evidence assessing the impact of obesity on DAS. We sought to investigate the influence of obesity on 1 year outcomes in a large international RA cohort.

Methods

Patients with a clinical diagnosis of RA with complete 6 and 12 month follow up from the METEOR Foundation International RA database were identified. The cohort was divided into early RA (eRA, disease duration <12 months) and established RA subgroups (disease duration ≥12 months). Patient demographics, DAS28, Health Assessment Questionnaire (HAQ) score and BMI were collected from the first recorded visit on the database. The cohorts were stratified into 4 categories by BMI: 1) Underweight <18.5, 2) Normal 18.5-24.9, 3) Overweight 25-29.9 and 4) Obese ≥30. Outcomes of interest were: good EULAR response (DAS28), low disease activity (DAS28 <3.2) and DAS28 remission (DAS28 <2.6) at follow up. Associations between BMI category and outcome measures at follow up (6 and 12 months) were explored using multivariate logistic regression analysis for both the eRA and established RA cohorts, adjusting for age, gender and smoking status.

Results

1,525 patients with complete data were identified. Mean age was 53.2 (SD 13.2) and 78.8% were female. The eRA and established RA subgroups contained 641 and 884 patients respectively, with a similar distribution of BMI categories seen in both groups (mean BMI 26.8 (SD 5.6) and 26.8 (SD 5.07) respectively).

At baseline median DAS28 scores for each BMI category were similar to those described for this cohort previously.¹Logistic regression analysis found no associations between overweight or obese BMI categories and clinical outcomes at 6 or 12 month follow up in the eRA subgroup. However, underweight patients had a lower probability of achieving low disease activity at 6 and 12 months (OR 0.24 (95%CI 0.07, 0.85) and OR 0.14 (95%CI 0.03, 0.62) respectively).

Analysis of the established RA subgroup identified obese patients to be significantly less likely to exhibit low disease activity at 6 and 12 month follow up, or disease remission at 12 months follow up (Table 1).

Table 1. Multivariate adjusted offs ratio (95% Confidence Intervals) for association between disease activity and BMI category for the established RA cohort.

Variable	Underweight (n=12)	Normal (r) (n=359)	Overweight (n=313)	Obese (n=200)
Good Response 6 months	0.42 (0.05, 3.37)	1.0	0.90 (0.60, 1.35)	0.59 (0.36, 0.97)
DAS28 <3.2 at 6 months	1.23 (0.38, 3.99)	1.0	0.83 (0.60, 1.13)	0.55 (0.39, 0.80)
DAS28 <2.6 at 6 months	0.62 (0.16, 2.38)	1.0	0.84 (0.60, 1.16)	0.48 (0.32, 0.72)
Good Response 12 months	0.39 (0.05, 3.15)	1.0	0.80 (0.54, 1.20)	0.97 (0.63, 1.52)
DAS28 <3.2 at 12 months	1.89 (0.55, 6.48)	1.0	1.12 (0.82, 1.53)	0.77 (0.54, 1.10)
DAS28 <2.6 at 12 months	0.97 (0.28, 3.38)	1.0	0.86 (0.62, 1.20)	0.62 (0.42, 0.92)

Conclusion

Obese patients with RA appear to respond to treatment, and achieve treatment goals within the first year following diagnosis. Outside of this period, obese patients are less likely to reach low disease activity or disease remission. These findings may have important implications for treatment objectives in modern target based regimens.

References

¹Sparks CR, Moots RJ, Goodson NJ. OBESITY AND DISEASE ACTIVITY IN A LARGE INTERNATIONAL RHEUMATOID ARTHRITIS COHORT. Ann Rheum Dis 2014;73(Suppl 2):136-137

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