Persistence with Statins and Onset of Rheumatoid Arthritis: A Population-Based Cohort Study

In a retrospective cohort study, Gabriel Chodick and colleagues find a significant association between persistence with statin therapy and reduced risk of developing rheumatoid arthritis, but only a modest decrease in risk of osteoarthritis. 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. 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. : Please see later in the article for the Editors' Summary Background: The role of statins in the management of diseases that have an inflammatory component is unclear. There is some evidence that statins may have anti-inflammatory and immunumodulatory properties, demonstrated by reducing the level of C-reactive protein that may play an important role in chronic inflammatory diseases, such as rheumatoid arthritis—a chronic condition that is a major cause of disability. Some small studies have suggested a modest effect of statins in decreasing disease activity in patients with rheumatoid arthritis, but a recent larger study involving over 30,000 patients with rheumatoid arthritis showed no beneficial effect. Furthermore, it has been suggested that statins may have a role in the primary prevention of rheumatoid arthritis, but so far there has been no solid evidence base to support this hypothesis. Before statins can potentially be included in the treatment options for rheumatoid arthritis, or possibly prescribed for the prevention of this condition, there needs to be a much stronger evidence base, such as larger studies with longer follow-up periods, which clearly demonstrates any significant clinical benefits of statin use. Why Was This Study Done?: This large study (more than 200,000 patients) with a long follow-up period (average of 10 years) was conducted to discover whether there was any kind of association between persistent use of statins and the onset of rheumatoid arthritis. What Did the Researchers Do and Find?: The researchers conducted a retrospective cohort study among the members of Maccabi Healthcare Services (a health maintenance organization [HMO]) in Israel, which has 1.8-million enrollees and covers every section of the Israeli population, to identify statin users who were at least 18 years of age and did not have RA or a related disease at study entry. The cohort covered the period 1998–2007 and included members who were continuously enrolled in the HMO from 1995 to 1998. The researchers then analyzed the incidence of newly diagnosed rheumatoid arthritis, recording the date of first diagnostic codes (International Classification of Diseases, 9th revision [ICD-9]) associated with rheumatoid arthritis during the study follow-up period. To assess any potential effects of “healthy adherer” bias (good adherence to medication in patients with a chronic illness may be more likely to lead to better health and improved survival), the researchers also examined any possible association between persistent statin use and the development of osteoarthritis, a common degenerative joint disease that is unlikely to be affected by statin use. What Do These Findings Mean?: This study suggests that there is an association between persistence with statin therapy and reduced risk of developing rheumatoid arthritis. Although the researchers took into account the possibility of healthy adherer bias (by comparing results with the osteoarthritis cohort), this study has other limitations, such as the retrospective design, and the nonrandomization of statin use, which could affect the interpretation of the results. However, the observed associations were greater than those that would be expected from methodological biases alone. Larger, systematic, controlled, prospective studies with high efficacy statins, particularly in younger adults who are at increased risk for rheumatoid arthritis, are needed to confirm these findings and to clarify the exact nature of the biological relationship between adherence to statin therapy and the incidence of rheumatoid arthritis. Additional Information: Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000336.