Photo: Thomas Griezbeck
Taking oral contraceptives is associated with a lowered risk of developing rheumatoid arthritis, finds a new observational study by researchers at Karolinska Institutet published in Annals of the Rheumatic Diseases. But no significant link was found for breastfeeding after accounting for various potentially influential factors.
The researchers analysed data from the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) to find out if there is a link between the development of rheumatoid arthritis and use of oral contraceptives and/or breastfeeding among adult women who had had at least one child. The study included women aged 18 and above, living in defined areas of Sweden between 1996 and 2014. During this timeframe, 2641 women were diagnosed with rheumatoid arthritis. 4251 women randomly selected from the general population and matched for age acted as a control group.
Significantly reduced risk
The women were asked about their contraceptive and reproductive histories, their lifestyle, their education and whether they had breastfed their children. In addition, blood samples were taken to check for ACPA (anti-citrullinated protein) antibodies. Nine out of 10 people who test positive for ACPA antibodies will have rheumatoid arthritis, and the presence of these antibodies may indicate more serious disease.
The risk of developing ACPA-positive rheumatoid arthritis was 15 per cent lower in current users of oral contraceptives and 13 per cent lower in past users compared with women who had never used an oral contraceptive. Using the Pill for more than seven years was associated with a 19 per cent lower risk of developing both ACPA-positive and ACPA-negative rheumatoid arthritis. However, no firm conclusions can be drawn about cause and effect in an observational study, and the researchers lacked information about the dose or type of oral contraceptive.
Breastfeeding did not have the same effect
Although a lower risk was also found among women who had breastfed at least one child, this was not significant after having accounted for potentially influential factors.
Reference: Oral contraceptives, breastfeeding and the risk of developing rheumatoid arthritis: results from the Swedish EIRA study Annals of the Rheumatic Diseases, online august (2017)