Background Ankylosing spondylyitis (AS) and Psoriatic arthritis (PsA) have been associated with increased risk of myocardial infarction (MI). Diclofenac use has been associated with MI in the general population and is commonly used in spondyloarthropathy (SpA) patients. However data on risk of MI with diclofenac use in the SpA population are not available.

Objectives To examine the relation between diclofenac use and the risk of MI among SpA patients.

Methods Using 1995-2012 data from The Health Improvement Network, a database of medical records from general practitioners in the United Kingdom, we identified patients with incident AS or PsA who had no history of ischemic heart disease or MI. Eligibility criteria included age 18-89 years, >1 year enrollment in THIN prior to SpA diagnosis, and ≥1 prescription for an NSAID (never users excluded to minimize confounding by indication). We identified subjects prescribed diclofenac after SpA diagnosis and generated a diclofenac-exposed cohort. We selected subjects who were not currently exposed to diclofenac for inclusion in the comparator cohort. We used Cox proportional hazards regression models to calculate multivariable-adjusted hazard ratios (HRs) for incident MI. We conducted the equivalent cohort analyses for naproxen users (a negative control) and rofecoxib users (a positive control).

Results Among individuals with incident AS or PsA, we identified 3480, 2176, and 527 incident users of diclofenac, naproxen and rofecoxib, respectively. Within the 3 cohorts studied, AS was present in 28-32% and 44-49% of all subjects were female. Crude incidence rate ratios for MI were 1.25 (0.86, 1.84) in the diclofenac cohort, 1.20 (0.78, 1.85) in the naproxen cohort, and 2.34 (1.24, 4.43) in the rofecoxib cohort relative to non-use. After multivariable adjustment, the hazard ratio for MI was 1.61 (1.08, 2.40) for diclofenac, 1.40 (0.90, 2.19) for naproxen, and 2.60 (1.30, 5.22) for rofecoxib (Table) compared with non-use. Restriction to AS subjects led to similar effect estimates, but did not reach statistical significance due to small numbers.

Conclusions Diclofenac use among SpA patients was associated with a 61% increased risk of MI relative to non-use, while naproxen use was not associated with increased risk. Diclofenac use in persons with AS or PsA may increase MI risk beyond that associated with the underlying inflammatory disease.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.1665