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5 November 2004
Rheumatoid Arthritis Risk Tied To Hormonal Events 
A team of researchers led by Elizabeth Karlson, at Brigham and Women's Hospital in Boston, has been studying the relationship between hormones and the risk of developing rheumatoid arthritis. Their findings, published in Arthritis & Rheumatism, strongly support the lasting benefits of breastfeeding in protecting against the disease. The researchers also identified irregular menstrual cycles as a new risk factor for rheumatoid arthritis. Looking at total lifetime breastfeeding, regardless of number of children, women who had breast-fed for between 13 and 23 months had a 20 percent reduction in the risk of rheumatoid arthritis compared with women who did not breastfeed. Women who had breast-fed for at least 24 months increased their risk reduction to 50 percent. "Our data suggest breast-feeding confers long lasting protection against developing rheumatoid arthritis," Karlson states, "because the mean time since the last pregnancy among women with rheumatoid arthritis was 25 years." In addition, women who experienced irregular menstrual cycles between the ages of 20 and 35 were shown to have an increased risk of rheumatoid arthritis. The study did not show any association between a history of oral contraceptive use and disease risk, or any significant differences in disease risk related to a woman's number of pregnancies. The researchers confirmed that the risk of rheumatoid arthritis increases with age and demonstrated a peak risk at the typical time of menopause. Because the onset of rheumatoid arthritis often coincides with menopause, some studies have linked the disease to falling estrogen levels, indicating the potential benefits of estrogen therapy. In this study, however, estrogen therapy among postmenopausal women did not protect against rheumatoid arthritis. "These findings suggest avenues for further research into the hormonal mechanisms involved in rheumatoid arthritis, because the complex relationships between rheumatoid arthritis and reproductive hormones clearly warrant further study," Karlson concludes.
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