THURSDAY, Nov. 4, 2004 (HealthDayNews) -- Breast-feeding offers a host of health benefits for the baby, but a new study says it may help the mother avoid rheumatoid arthritis as well.
The study, which appears in the November issue of Arthritis and Rheumatism, found that women who breast-fed for more than 24 months reduced their risk of developing rheumatoid arthritis by 50 percent compared to women who elected not to nurse their children.
The study also found that women with irregular menstrual cycles had a higher risk of rheumatoid arthritis than women with regular periods.
"I think the most important finding is that breast-feeding is protective against the future risk of rheumatoid arthritis," said study co-author Dr. Elizabeth Karlson, an assistant professor of medicine at the Harvard School of Medicine and Brigham and Women's Hospital in Boston.
Rheumatoid arthritis affects 2.1 million Americans, according to the Arthritis Foundation. It is a chronic disease that causes inflammation in the lining of the joints. Symptoms include swelling, redness, warmth and stiffness of affected joints. As the disease progresses, joints become permanently damaged, and may result in loss of movement.
Karlson's research was part of the prospective Nurses' Health Study, which includes a cohort of more than 120,000 women. From that large group, Karlson and her colleagues contacted 11,674 women, and 9,031 responded. During the 26 years included in this study, Karlson said that 674 women were diagnosed with rheumatoid arthritis.
The age of the women at the time of the diagnosis varied greatly, between 30 and 79 years old.
The researchers gathered information about age, body mass index, smoking history, the age menstruation began, how many children the women had, how many months in total they spent breast-feeding, use of contraception or hormone replacement therapy, age at menopause, and whether menstrual cycles were regular.
They found that in women who nursed for four to 11 months, their risk of rheumatoid arthritis was reduced by 10 percent. Women who breast-fed between 12 and 23 months total had a 20 percent reduction in risk. If a woman spent more than 24 months of her life breast-feeding her children, the risk of rheumatoid arthritis dropped dramatically -- by 50 percent.
The study also found that women with irregular menstrual cycles had a 40 percent greater risk of developing rheumatoid arthritis.
Karlson said hormonal factors were likely involved with the changes in risk, though the researchers aren't sure how hormones are affecting the risk of rheumatoid arthritis.
The researchers also found that women between the ages of 50 and 54 had an increased risk of developing rheumatoid arthritis, and that those ages often coincided with the onset of menopause, suggesting hormonal factors again.
"This is a large group and it gives us more information to give young women," said Dr. Stephen Lindsey, head of rheumatology at the Ochsner Clinic Foundation Hospital in New Orleans.
Lindsey explained that rheumatoid arthritis has a genetic component to it, so this information could be useful for women with the disease to pass down to their daughters who may still be in their childbearing years.
"If it's in your family and you get pregnant, I would advise a woman to breast-feed," he said.
There's not much women can do about irregular menstrual cycles, according to Karlson. She said they didn't find a reduction in risk from birth control pill use, so she doubts that using the pill to regulate a period would help. Lindsey said, though, that if a woman were already thinking about using oral contraceptives to regulate her cycle, and she has rheumatoid arthritis in her family, "this information might tip the scales in their favor."
Another important risk factor that wasn't addressed in this study, added Lindsey, is cigarette smoking, and he advised women to stop smoking.
To learn more about rheumatoid arthritis, visit the Arthritis Foundation.