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Breastfeeding halves a mother’s risk of developing rheumatoid arthritis (RA), Rheumatology reports.

Researchers enrolled 7,349 women in China aged, on average, 63.5 years. Depending on the definition, 9.1 or 3.4 per cent of the women had RA. Breastfeeding was associated with a 51-55 per cent reduction in RA risk compared with women who did not breastfeed. RA risk declined with increasing duration of breastfeeding – from 16-19 per cent for one to 11 months to 46 per cent after at least 36 months. Oral contraceptives did not influence RA risk. 

The authors point out that levels of progesterone, which is anti-inflammatory, increase during pregnancy and remain high throughout breastfeeding. Furthermore, levels of cortisol, which is also anti-inflammatory, are higher among post-menopausal women who breastfed and concentrations rise with longer duration of breastfeeding. More speculatively, prolonged breastfeeding may reduce concentrations of persistent organic pollutants, which seem to influence the immune system and, therefore, increase RA risk.

Further studies are needed to elucidate the mechanisms. (Rheumatology)