Objectives: The impact of body mass index (BMI) on cardiovascular risk in rheumatoid arthritis (RA) is unclear. RA characteristics may influence the association between BMI and risk. Disease activity, which predicts cardiovascular risk, is associated with obesity only among anticitrullinated antibody (ACPA)-positive patients. Biologics alter body composition and mitigate cardiovascular risk in RA. We explored the association of BMI with cardiovascular risk and whether this varied across ACPA status and biologic use.

Methods: We evaluated 3982 patients from an international observational cohort. Outcomes included (a) first major adverse cardiovascular event (MACE) encompassing myocardial infarction, stroke or cardiovascular death; and (b) all events comprising MACE, angina, revascularisation, transient ischaemic attack, peripheral arterial disease and heart failure. Multivariable Cox models stratified by centre risk evaluated the impact of BMI, ACPA, biologics and their two- and three-way interactions on outcomes.

Results: We recorded 192 MACE and 319 total events. No main effects of BMI, ACPA or biologics were observed. A three-way interaction between them on MACE (p-interaction<0.001) and all events (p-interaction=0.028) was noted. Among ACPA negative patients, BMI was inversely associated with MACE (HR 0.38 (95% CI 0.25 to 0.57)) and all events (HR 0.67 (0.49 to 0.92)) in biologic users but not non-users (p-for-interaction <0.001 and 0.012). Among ACPA-positive patients, BMI was associated with MACE (HR 1.04 [1.01–1.07]) and all events (HR 1.03 (1.00 to 1.06)) independently of biologic use.

Conclusions: BMI is inversely associated with cardiovascular risk only among ACPA-negative biologic users. In contrast, BMI is associated with cardiovascular risk in ACPA-positive patients independently of biologic use.