Obesity is a risk factor for poor response to treatment in early rheumatoid arthritis - a NORD-STAR analysis

Objective. This report from the NORD-STAR trial aimed to determine if obesity is associated with response to conventional and biological anti-rheumatic treatment in early rheumatoid arthritis (RA).
Methods. This report included 793 participants with untreated early RA from the randomized, longitudinal NORD-STAR trial, all of whom had their body mass index (BMI) assessed at baseline. Obesity was defined as BMI ≥30 kg/m2. All participants were randomized 1:1:1:1 to one of four treatment arms: active conventional treatment, certolizumab-pegol, abatacept, and tocilizumab. Clinical and laboratory measurements were performed at baseline and at 8-, 12-, 24, and 48-week follow-up. The primary endpoint for this report was response to treatment based on CDAI and SDAI remission and DAS28-CRP<2.6 stratified by BMI.
Results. Out of 793 people included in the present report, 161 (20%) had obesity at baseline. During follow-up, participants with baseline obesity had higher disease activity compared to those with lower BMI, despite having similar disease activity at baseline. In survival analyses, obesity was associated with a lower likelihood of achieving response to treatment during follow-up for up to 48 weeks (CDAI remission, HR 0.84, 95% CI 0.67-1.05; SDAI, HR 0.77, 95% CI 0.62-0.97; DAS28-CRP<2.6, HR 0.78, 95% CI 0.64-0.95). The effect of obesity on response to treatment was not influenced by the treatment arms.
Conclusion. In people with untreated early RA followed up for up to 48 weeks, obesity was associated with a lower likelihood of good treatment response, irrespective of the type of randomized treatment received.