Researchers have carefully examined the relationship between oral contraceptive pills and developing arthritis and determine whether contraceptive users have a lower risk.
A recent study published in the Annals of Rheumatic Diseases found that women who have used oral contraceptive pills had a significantly reduced risk of developing ACPA-positive rheumatoid arthritis (RA). The risk of developing ACPA-positive and ACPA-negative rheumatoid arthritis was decreased in women who used oral contraceptive pills for more than seven years. Since this disease is more prevalent in women than in men, studying the use of oral contraceptive pills and the risk of developing RA might suggest a hormonal influence.
The results of this study were derived from the Swedish Epidemiological Investigation of Rheumatoid Arthritis(EIRA). This study was one of the largest case-control studies comprising of women 18 years and older and incident cases of RA. The participating women answered an extensive questionnaire regarding lifestyle, environmental exposures, including oral contraceptive pill use, breastfeeding, and other potential confounders, such as alcohol consumption and smoking status. For analysis of oral contraceptive pill use, 2,578 cases of RA and 4,129 controls were available. Oral contraceptive users were divided into several groups relative to their contraceptive use. “Current” users were defined as women who were actively taking OC and had been for more than one year. “Past” users were women who stopped taking OC more than one year ago. “Ever” users included both past and current users, while “never” users included women who had never taken OC.
Between oral contraceptive users and non-users, the ever users had a decreased risk of developing RA. Similar results were found among current users and past users of oral contraceptive pills. A dose-response was detected with oral contraceptive use and decreased risk of development of RA. Women who used oral contraceptives for more than 7 years had a decreased risk of both ACPA-positive and ACPA-negative RA.
A secondary outcome of the study was the interaction between smoking status and oral contraceptive use and the risk of developing ACPA-positive RA. Smokers who did not use OC had an odds ratio of 2.34 whereas smokers who did use OC had an odds ratio of 1.71. This indicates a possible protective mechanism against ACPA-positive RA with oral contraceptive use in women who smoke. However, since oral contraceptive use and smoking has been linked to blood clots, women who are smokers may be less likely to have oral contraceptive pills prescribed to them. This fact presents a limitation to the analysis since women who smoke have a higher ACPA-positive RA risk and may avoid oral contraceptive use.
Rheumatoid arthritis is a complex disease that is not fully understood. The higher prevalence in woman suggests a hormonal influence. The use of oral contraceptive pills seems to decrease the risk of RA, especially when used for over 7 years. This was the largest study to date examining these risks and as such was able to address these questions more thoroughly than ever before. This study will prompt further investigations on the biological mechanisms of the hormonal factors on developing RA.
Written by Jessica Caporuscio, PharmD
Orellana C, Saevarsdottir S, Klareskog L, et al. Oral contraceptives, breastfeeding and the risk of developing rheumatoid arthritis: results from the Swedish EIRA study. Ann Rheum Dis. 2017.