Women who take the contraceptive pill may be less likely to develop rheumatoid arthritis (RA), new research suggests.
A study published online in the Annals of the Rheumatic Diseases found a link between oral contraceptives and a lower risk of developing the disease, particularly in women who take the pill for seven or more consecutive years.
But the study found no significant link between breastfeeding and a lower risk of developing rheumatoid arthritis, after accounting for various potentially influential factors. Breastfeeding has previously been associated with a protective effect when it comes to RA.
Rheumatoid arthritis is two to three times more common in women than in men, and it is thought hormonal and reproductive factors may partly explain this gender difference.
For the new study, researchers used data from the Swedish Epidemiological Investigation of Rheumatoid Arthritis on 2,809 women who had been diagnosed with rheumatoid arthritis, and another 5,312 women without the disease from the general population.
They found that women who had used an oral contraceptive at any time had a lower risk of developing rheumatoid arthritis than those who had never done so. The risk was 15% lower in current users of the pill and 13% lower in past users.
And the association was significant for women who tested positive for anti-citrullinated protein antibodies (ACPA). Nine out of 10 people who test positive for ACPA will have rheumatoid arthritis, and the presence of these antibodies may indicate more serious disease.
Overall, using the pill for more than seven years — the average length of use among the study participants — was associated with a 19% lower risk of developing RA, regardless of whether the women tested positive or negative for ACPA.
Although a lower risk was also found among women who had breastfed at least one child, this was not significant after other potentially influential factors were accounted for.
“Further research is required to explore the biological mechanisms behind our findings and whether hormonal factors have different impact on the ACPA-subsets of rheumatoid arthritis,” the researchers said.