Women who breastfeed are less likely to develop rheumatoid arthritis than women who don’t, according to a new report.

“Lower risk of rheumatoid arthritis is a likely additional health benefit of breastfeeding, in addition to lowering the risk of ovarian cancer and breast cancer,” Dr. Elizabeth Wood Karlson from Brigham and Women’s Hospital, Boston, told AMN Health.

Karlson and her colleagues used data from the Nurses’ Health Study to explore the contribution of women’s hormonal factors on the subsequent development of arthritis.

Women who breastfed for a total of 12 to 23 months during their lifetime had a 30 percent reduction in the risk of rheumatoid arthritis, the authors report, and those who breastfed for at least 24 months had a 50 percent reduction in risk.

On the other hand, very irregular menstrual cycles and starting periods at an early age (by age 10 years) were associated with an increased risk of rheumatoid arthritis, the report in the medical journal Arthritis & Rheumatism indicates.

Oral contraceptive use, the number of children a woman had, and her age at first birth had no effect on the odds of developing arthritis.

“We are currently conducting a study of levels of hormones in blood samples collected from women in the Nurses’ Health Study in 1989,” Karlson added.

Specifically, she explained, “We will be studying levels of prolactin and androgen hormones in women who did not have rheumatoid arthritis at the time of the blood sample, but later developed rheumatoid arthritis, compared to hormone levels in women who never developed rheumatoid arthritis.”

SOURCE: Arthritis & Rheumatism, November 2004.