Stockholm, Sweden—A decreased risk of developing rheumatoid arthritis has been added to the list of additional benefits for longer-term use of oral contraceptive (OC) pills.

Taking the contraceptive pill, particularly for 7 or more consecutive years, is linked to a lowered risk of developing rheumatoid arthritis (RA), a new study finds. The research published online in the Annals of the Rheumatic Diseases said, however, that no protective effect was determined for breastfeeding (BF), after accounting for various potentially influential factors, the findings show.

Background information in the article notes that hormonal and reproductive factors have been suspected to play a role in RA because the chronic disease is two to three times as common in women as it is in men. Research on that hypothesis has been mixed, according to Swedish researchers, who sought to look at the issues in more depth.

The Karolinska Institutet researchers focused on the development of the disease and use of OCs and/or breastfeeding among adult women who had had at least one child. To do that, they employed data from the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA).

The database includes women aged 18 years and older living in a defined area of Sweden between 1996 and 2014. Included in the final analysis were 2,578 women with RA and 4,129 women from the comparison group who did not have RA. Of these, 884 with RA and 1,949 from the comparison group had breastfed at least one child between 2006 and 2014.

Investigators drew blood samples to check for anticitrullinated protein antibodies (ACPA), which in nine out of 10 people indicates RA, and possibly a more serious presentation of the disease. The women provided information about their contraceptive and reproductive histories, their lifestyles, whether they had breastfed their children, and their educational levels.

Results suggest that, compared with never users, ever and past OC users had a decreased risk of ACPA-positive RA (OR=0.84 [95% CI 0.74 to 0.96]; OR=0.83 [95% CI 0.73 to 0.95], respectively). No significant associations were found for ACPA-negative RA.

The risk was 15% lower in current users of OCs and 13% lower in past users, with a significant association for women who tested positive for ACPA antibodies, even after taking into account tobacco and alcohol consumption.

Long duration of OC use—greater than 7 years, versus never-use—decreased the risk of both ACPA-positive (P = 0.0037) and ACPA-negative RA (P = 0.0356).

A significant interaction was observed between the lack of OC use and smoking (AP=0.28 [95% CI 0.14–0.42]) on the risk of ACPA-positive RA, but no interactions were found for BF.

A history of long BF, meanwhile, decreased the risk only of ACPA-positive RA in a dose-dependent manner (P = 0.0086), but the trend did not remain after adjustments, according to study authors

Study authors cautioned that the study was observational, so no cause-and-effect conclusions can be drawn. They also pointed out, however, that the number of participants was large and the study accounted for a range of factors that could affect outcomes.

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