Oral contraceptives linked to reduced risk of rheumatoid arthritis

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, 2809 women were diagnosed with rheumatoid arthritis. 5312 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.

The study was carried out by Cecilia Orellana at the Department of Clinical Neuroscience and Camilla Bengtsson at the Institute of Environmental Medicine, Karolinska Institutet, among others. The research was supported by grants from the Swedish Research Council, the Swedish Research Council for Health, Working Life and Welfare, King Gustav V’s 80-year foundation, Vinnova, the Swedish Foundation for Strategic Research, the Swedish Rheumatic Foundation, the Stockholm County Council, the Insurance Company AFA, the Innovative Medicines Initiative-supported BTCure project, and the National Institutes of Health.

This news article is based on a press release from Annals of the Rheumatic Diseases.

Publication

Cecilia Orellana, Saedis Saevarsdottir, Lars Klareskog, Elizabeth W. Karlson, Lars Alfredsson and Camilla Bengtsson. “Oral contraceptives, breastfeeding and the risk of developing rheumatoid arthritis: results from the Swedish EIRA study”. Annals of the Rheumatic Diseases, online 17 August 2017. doi 10.1136/annrheumdis-2017-211620