Background: The beneficial effects of statins in rheumatoid arthritis (RA) have been suggested previously, but it is unclear whether statins may prevent its development. The aim of this retrospective cohort study was to explore whether persistent use of statins is associated with onset of RA.
Methods and findings: The computerized medical databases of a large health organization in Israel were used to identify diagnosed RA cases among adults who began statin therapy between 1998 and 2007. Persistence with statins was assessed by calculating the mean proportion of follow-up days covered (PDC) with statins for every study participant. To assess the possible effects of healthy user bias, we also examined the risk of osteoarthritis (OA), a common degenerative joint disease that is unlikely to be affected by use of statins. A total of 211,627 and 193,770 individuals were eligible for the RA and OA cohort analyses, respectively. During the study follow-up period, there were 2,578 incident RA cases (3.07 per 1,000 person-years) and 17,878 incident OA cases (24.34 per 1,000 person-years). The crude incidence density rate of RA among nonpersistent patients (PDC level of <20%) was 51% higher (3.89 per 1,000 person-years) compared to highly persistent patients who were covered with statins for at least 80% of the follow-up period. After adjustment for potential confounders, highly persistent patients had a hazard ratio of 0.58 (95% confidence interval 0.52-0.65) for RA compared with nonpersistent patients. Larger differences were observed in younger patients and in patients initiating treatment with high efficacy statins. In the OA cohort analysis, high persistence with statins was associated only with a modest decrement in risk ratio (hazard ratio = 0.85; 0.81-0.88) compared to nonadherent patients.
Conclusions: The present study demonstrates an association between persistence with statin therapy and reduced risk of developing RA. The relationship between continuation of statin use and OA onset was weak and limited to patients with short-term follow-up.