Seven or more years of oral contraceptive use was linked to a 19% reduced risk of rheumatoid arthritis.
Findings from a large study suggest that the hormonal contraceptive pill may reduce the risk of developing rheumatoid arthritis (RA). Taking oral contraceptives for 7 or more years was linked to the lowest risk of RA, according to the study, published by the Annals of the Rheumatic Diseases.
While RA is known to commonly affect the joints in the knees, hands, and wrists, it can also affect the lungs, heart, eyes, and other body parts. Chronic inflammation can erode the joint lining and tissue, resulting in pain, deformity, and unsteadiness.
Hormonal and reproductive factors have been thought to cause the sex disparity, making women more likely than men to develop RA; however, the evidence has been mixed, according to the authors.
Previous studies have investigated RA and the contraceptive pill, but many have not been able to show a significant association. Other studies have shown a positive link between breastfeeding and RA, while others show a negative link. The authors hypothesize the non-conclusive findings were lacking due to not accounting for seropositivity.
In the new study, the authors assessed the link between oral contraceptives, breastfeeding, and RA among women who had given birth to at least 1 child. Included in the study were 2578 women with RA and 4129 controls living in Sweden between 1996 and 2014.
The authors examined blood samples for the biomarker anti-citrullinated protein antibodies (ACPAs), which are present in the blood of 90% of patients with RA. This biomarker may indicate disease severity as well.
The investigators also examined data about reproductive history, lifestyle, breastfeeding history, and education levels.
The authors found that 884 women with RA and 1949 controls breastfed 1 or more children between 2006 and 2014, according to the study.
The authors also discovered that patients who had taken the contraceptive pill showed a reduced risk of RA compared with those who had never used it.
Specifically, current use of the contraceptive pill reduced the risk of RA by 15%, while past use was linked to a 13% reduction, according to the study.
The researchers found that the association was significant among patients who tested positive for APCAs, even after accounting for other risk factors.
Notably, patients who used the contraceptive pill for more than 7 years had a 19% lower risk of developing RA, even among patients negative for ACPAs. These findings suggest that there may be a dose-response effect for oral contraceptives and RA, according to the study.
Similar results were noted among women who had breastfed; however, these results were not found to be statistically significant.
The authors caution that the study was not designed to determine cause and effect, but it did include a large number or patients and accounted for other factors.
“In this large population-based case-control study of incident RA [rheumatoid arthritis], with careful matching between cases and controls and extensive exposure information, we found that women who had ever used OCs [oral contraceptives] had a significantly decreased risk of developing RA,” the authors concluded.