Results of an observational study presented by lead (researcher) Mitra Keshavarz, MD, Malmö Hospital University, Sweden, indicated that breast feeding for a period of 13 months or more reduced a woman's risk of developing rheumatoid arthritis (RA).

Data for this study was derived from a community-based health study incorporating information from the Swedish National Hospital Discharge and the National Cause of Death Register. Health information from 136 women who later developed RA was compared with that of 544 controls. Information on the use of oral contraceptives, hormone replacement therapy, and other lifestyle factors was derived from a self-administered questionnaire.

The mean age of onset of RA was 63.3, years with a median duration of 5.5 years from enrolment in the health study to RA onset. Longer history of breast-feeding was associated with a reduced risk of RA (OR: 0.46; 95% CI 0.24–0.91 for women with ≥13 months of breast-feeding, and OR 0.74; 95% CI 0.45–1.20 for those with 1–12 months, vs those who never breastfed).

The protective effect of longer breast-feeding remained significant when adjusted for parity and either smoking or level of education in multivariate models. Parity, oral contraceptive use, or hormonal replacement therapy, were not significantly associated with future development of RA.

“This study specifically highlights the potential of naturally-induced hormones in protecting individuals from developing rheumatoid arthritis in the future. Furthermore, it adds to the growing body of evidence in favor of breast feeding and its positive health implications,” said Dr. Keshavarz.