• Rheumatoid Arthritis
• Outcomes Research
• Health Services Research

We read with interest the recent paper by Sandberg et al1 highlighting the negative impact of obesity on disease remission in a cohort of patients with early rheumatoid arthritis (RA).

We have investigated the impact of both obesity and comorbidity on disease remission in an established RA cohort. Data were collected prospectively between 2003 and 2011 from the Haywood Hospital, North Staffordshire, UK. Patients fulfilled the 1987 American College of Rheumatology criteria for RA,2 had been followed up for 3 years and were taking conventional (non-biologic disease-modifying antirheumatic drugs (DMARDs)) at baseline. Participants underwent an annual standardised research assessment, separate to their routine clinical care, including demographics, body mass index (BMI) and disease activity using Disease Activity Score in 28 Joints (DAS28).3 Comorbidity burden was measured using the age-adjusted Charlson index.4 ,5 DMARD treatment was at the discretion of the rheumatologist. Remission was defined as a DAS28 of <2.6.3 Patients were characterised as ‘ever’ or ‘never’ achieving remission with sustained remission defined as a DAS28 of <2.6 at two consecutive time points. Comparison of clinical and demographic factors according to remission status was carried out using Student t test or Mann–Whitney U test and logistic regression. Ethics approval was obtained.

Three hundred and forty-three patients with RA with a mean (SD) age of 61.2 (10.8) years and mean (SD) disease duration of 10.3 (9.6) years were included. Two hundred and thirty-six (68.8%) were women. Remission prevalence was low, 44/343 (12.8%) at baseline, 48/288 (16.7%) at 1 year, 53/279 (19.0%) at 2 years and 49/245 (20.0%) at 3 years. Only 44/295 patients (14.9%) achieved a sustained remission. Complete 3-year follow-up data were obtained on 233 (68%) patients.

Patients ever achieving remission were younger (58.7 vs 62.8 years, p=0.003), men (OR 1.79, 95% CI 1.01 to 3.12, p=0.048), rheumatoid factor (RF) negative (OR 2.78, 95% CI 1.64 to 4.76, p<0.0001) and had a lower Charlson score (score 2 (1–3) vs 3 (2–4), p=0.0006) (table 1). Patients with obesity (BMI≥30) were less likely to achieve remission within 1 year (3.0% vs 13.0%, OR 0.25, 95% CI 0.07 to 0.95) or achieve sustained remission (8.0% vs 17.8%, OR 0.43, 95% CI 0.19 to 0.97).

Multivariate logistic regression analysis showed that obesity and comorbidity were independently associated with a failure to achieve remission during the 3-year follow-up. Increasing age, female sex and RF positivity were also significantly associated with a greater likelihood of failure to achieve remission (table 2).

Thus within this established RA cohort remission prevalence is low. As in early RA,1 obesity was associated with a failure to achieve remission. Although obesity is often associated with significant comorbidities, in this cohort no significant association was found between obesity and comorbidity, with both factors independently associated with lack of remission. This suggests that RA remission can be significantly influenced by clinical factors other than those usually considered in the rheumatoid disease process. The reason for these observations may involve increased C-reactive protein and cytokine levels seen in patients with adiposity,6 but further work is needed to determine the exact mechanisms involved.