Pattern of risks of rheumatoid arthritis among patients using statins: A cohort study with the clinical practice research datalink

Background: Previous studies evaluating the effect of statins on developing rheumatoid arthritis (RA) have shown conflicting results. Objectives: To examine the association between statin use and the risk of RA in a large population-based cohort in the United Kingdom (UK), with a special focus on describing the patterns of risks of RA during statin exposure. Methods: A retrospective cohort study using the UK Clinical Practice Research Datalink was conducted. All patients aged ≥40 years, who had at least one prescription of statins during the period 1995-2009 were selected and matched by age, sex and date of first prescription of statins to controls (patients not using statins). All patients were followed up for the development of RA. Patients were considered as having a diagnosis of RA if the first-time diagnosis registered by general practitioners was verified by the use of at least one prescription of disease modifying anti-rheumatic drugs.The follow-up period of statin users was divided into periods of current, recent and past exposure, with patients moving between these three exposure categories over time. Time-dependent Cox models were used to derive hazard ratios of RA, adjusted for disease history and previous drug use. Results: The study population included 1,023,240 patients, of whom 511,620 received a prescription of statins. No associations were found between RA and current or past users of statins. However, in patients who currently used statins, there were substantial changes in the hazard rates of RA over time: hazard rates were increased shortly after the first prescription of statins and then gradually decreased to baseline level. The risk of developing RA was increased in patients who recently used statins, as compared to non-users (HRadj, 1.41; 95% CI: 1.12-1.79). Conclusions: The risk of RA is substantially increased in the first year after the start of statins and then diminishes to baseline level. These findings suggest that statins might accelerate disease onset in patients susceptible to developing RA. Alternatively, confounding by cardiovascular risk factors and diagnostic suspicion bias may have influenced the findings