Current and past use of oral contraceptives offers women a protective effect against RA, research published in the Annals of the Rheumatic Diseases journal suggests.
But researchers found ‘no significant link’ with breastfeeding, which has historically been associated with a protective effect against RA.
Because RA is two to three times more common in women than men, it is thought hormonal and reproductive factors may partly explain this gender difference.
The study looked at data on over 2,500 women with RA compared to 4,100 women without, matched for age.
Blood samples were taken from all participants to check for ACPA antibodies, strongly associated with RA, and women were quizzed ‘in depth about their contraceptive and reproductive histories’.
Nine out of 10 people who test positive for ACPA antibodies will have RA, and the presence of these antibodies may indicate more serious disease.
The results suggest women who had used an oral contraceptive at any time had a lower risk of developing RA than those who had never done so, with a 15% lower risk in current users of oral contraceptives and a 13% lower risk in past users.
Using them for more than seven years – the average length of use among the study participants – was associated with a 19% lower risk of developing RA.
The authors, from the Institute of Environmental Medicine in Stockholm, Sweden, said: ‘We found that women who had ever used oral contraceptives had a significantly decreased risk of developing RA. The estimates were similar for current and past use, although only significant in the larger group of past users.’