Women who breastfeed their babies cut their risk of developing rheumatoid arthritis in half, according to a large new study of middle-aged and elderly Chinese women.
The findings, published online in the journal Rheumatology, have important implications for women around the world, but especially in China – given its one-child policy and declining rates of breastfeeding.
About 1.5 million Americans have rheumatoid arthritis (RA), an autoimmune disease that attacks joint tissue and causes painful, often debilitating inflammation. As the disease progresses, many RA patients become significantly disabled and emotionally distressed. About 75% of those who suffer from RA are women, according to the American College of Rheumatology.
In the Chinese study, researchers gathered information from over 7,000 women in South China aged 50 years or older who were enrolled in the Guangzhou Biobank Cohort Study. Women who took part in the study were born in the 1940s and 1950s, before the one-child policy in China was introduced in the late 1970s, and at a time when breastfeeding was more prevalent.
Questionnaires were used to ask the women about their disease and lifestyle history, obstetric history, breastfeeding history, and use of oral contraceptives. They were also asked whether they had been diagnosed with RA, and were examined by a trained nurse to check their joints for any swelling or tenderness that may indicate RA.
Most of the women reported they had at least one live birth, and of those, over 95% had breastfed their child for at least one month. The mean number of live births per woman was 2.9 and did not differ between those with and without RA.
Among women who had at least one live birth, those who had breastfed were about half as likely to have RA. The risk of RA was even lower for women who breastfed their babies for longer periods of time.
Women with RA were significantly more likely to be overweight, less likely to have breastfed their children, and those who did breastfeed did so for shorter durations. They were also slightly more likely to have a lower level of education and to have smoked.
No relationship was found between the use of a contraceptive pill and RA.
“Although the beneficial effects of breastfeeding for the mother and child are widely known, the findings from this study have further important implications for policy and research,” wrote lead author Peymane Adab, a professor and senior clinical lecturer at the University of Birmingham in England.
“The anti-inflammatory effects of pregnancy-related hormones and the short-term beneficial effects in RA are well known. However, the longer-term effects of pregnancy and the benefits of lactation are less clear. One potential proposed mechanism is through progesterone, which is anti-inflammatory and the levels of which rise during pregnancy and continue to be high during breastfeeding, through receptors developed on lymphocytes. This may result in long-term protective effects.”
Another possibility, according to Adab, is related to the hormone cortisol, which also has anti-inflammatory effects and has been shown to be significantly higher among post-menopausal women who have breastfed.
The Chinese study comes on the heels of new research at the University of Pittsburgh showing that mortality rates are two times higher in postmenopausal women with RA.
The study of nearly 10,000 postmenopausal women found that cardiovascular disease and cancer were the main causes of death among women with RA.