Breastfeeding lowers risk of rheumatoid arthritis

Women who breastfeed their infants for 13 months or longer are less likely to develop rheumatoid arthritis, according to an article published online May 13 in the Annals of the Rheumatic Diseases.

Mitra Pikwer, of Malmo University Hospital in Malmo, Sweden, and colleagues investigated whether breastfeeding and oral contraceptives affected the future risk of rheumatoid arthritis in a community-based cohort of 18,326 Swedish women. Lifestyle factors obtained from self-administered questionnaires were compared in 136 women with rheumatoid arthritis and 544 age-matched controls.

Prolonged breastfeeding was associated with a reduced risk of rheumatoid arthritis, the investigators found. Compared to women who did not breastfeed, the odds ratio was 0.46 for women who breastfed for at least 13 months and 0.74 for women who breastfed for between 1 and 12 months. The protective effect of prolonged breast-feeding remained significant after controlling for smoking and educational level, the report indicates. Oral contraceptives did not impact risk, the researchers note.

"Possible explanations for the protective effect of breastfeeding include long-term immunomodulation, such as the development of progesterone receptors on lymphocytes, dysregulated hypothalamic-pituitary-adrenal access, and differences in cortisol concentrations," the authors write.

Pikwer M, Bergström U, Nilsson JA, et al. Breast-feeding, but not oral contraceptives, is associated with a reduced risk of rheumatoid arthritis. Ann Rheum Dis. Published Online First: 14 May 2008. doi:10.1136/ard.2007.084707.