A recent study published in the May issue of Annals of Rheumatic Diseases found that breastfeeding for more than a year reduced women’s risk for rheumatoid arthritis. Researchers also found that women taking oral contraceptives, reported in a previous study to be protective, offered no protection.

These findings add to a growing body of evidence for the many health benefits of breastfeeding for women and children. Release of the results, coincide with a US government breastfeeding-friendly worksite initiative that calls upon employers to improve their support for breastfeeding mothers in the workplace in an effort to extend the period of breastfeeding.

Study results
Dr. Mitra Pikwer and colleagues at Malmo University Hospital in Malmo, Sweden, compared 136 women aged 44-74 years who developed rheumatoid arthritis between 1991 and 1996 with a control group of 544 healthy women of similar age.

Each participant completed a questionnaire related to oral contraceptive use and breastfeeding. Eighty-one percent of the experimental group and 84 percent of the control group reported having used oral contraceptives. Thirty-two per cent of women with rheumatoid arthritis reported that they had never breastfed, compared with 25 per cent in the control group.

After adjusting for potential risk factors including education and smoking, the researchers found that women who had breastfed for 13 months or more were 54 per cent less likely to develop rheumatoid arthritis than women who had never breastfed. In addition, women who breastfed for at least a month had a 26 percent lower risk for rheumatoid arthritis.

Women who gave birth to more children tended to be at lower risk for rheumatoid arthritis, with a 13 percent reduction in risk for each child. The researchers found that breastfeeding was a more important factor in the development of rheumatoid arthritis, but stressed the fact that more research is needed.

“Taken altogether, these findings suggest different short-term and long-term effects of breastfeeding on the immune system and on susceptibility to rheumatoid arthritis,” said Pikwer.

How does breastfeeding protect against rheumatoid arthritis?
“The exact mechanism linking breastfeeding to a lower risk of rheumatoid arthritis is unknown, but it may be due to hormonal changes,” said Pikwer.

Female hormones are thought to play a role in the development of rheumatoid arthritis given that the incidence is twice as high among women compared to men. Additionally, rheumatoid arthritis often improves during pregnancy, suggesting a hormonal influence.

“The protective effect may arise from long-term immunomodulation through the development of progesterone receptors on lymphocytes, differences in cortisol concentrations, and other potential mechanisms,” he added.

Previous research suggested that breastfeeding was a risk factor for the development of rheumatoid arthritis in women. But this study differs in that it looks at longer-term risk and suggests that breastfeeding may have a dose-dependent response.