Mothers who breastfeed for at least 15 months over one or more pregnancies may be less likely to develop multiple sclerosis, a study has found.
Multiple sclerosis (MS) is a disease in which the insulating covers of nerve cells in the brain and spinal cord are damaged by the body's immune system.
"This is another example of a benefit to the mother from breastfeeding," said Annette Langer-Gould from health care company Kaiser Permanente Southern California in the US.
"Other health benefits include a reduced risk of breast cancer, ovarian cancer, type 2 diabetes and heart attack," said Langer-Gould.
Women with MS have significantly fewer relapses, or attacks, during pregnancy or while they are breastfeeding exclusively, meaning that the child receives only breast milk.
"Many experts have suggested that the levels of sex hormones are responsible for these findings, but we hypothesised that the lack of ovulation may play a role, so we wanted to see if having a longer time of breastfeeding or fewer total years when a woman is ovulating could be associated with the risk of MS," Langer-Gould said.
The study involved 397 women with an average age of 37 who were newly diagnosed with MS or its precursor, clinically isolated syndrome. They were compared to 433 women matched for race and age.
The women were given in-person questionnaires about pregnancies, breastfeeding, hormonal contraceptive use and other factors.
Women who had breastfed for a cumulative amount with one or more children for 15 months or more were 53 per cent less likely to develop MS or clinically isolated syndrome than women who had a total of zero to four months of breastfeeding.
A total of 85 of the healthy women had breastfed for 15 months or more, compared to 44 of the women with MS. For the healthy women, 110 breastfed for zero to four months, compared to 118 of the women with MS.
Women who were age 15 or older at the time of their first menstrual cycle were 44 per cent less likely to develop MS later than women who were 11 years old or younger at the time of their first menstruation. A total of 44 of the healthy women were 15 or older at first menstruation, compared to 27 of the women with MS. Additionally, 120 of the healthy women were 11 years old or younger at first menstruation, compared to 131 of the women with MS.
Researchers said that the study does not prove that breastfeeding is responsible for the reduced risk of MS; it only shows the association.
"This study provides more evidence that women who are able to breastfeed their infants should be supported in doing so," Langer-Gould said.
"Among the many other benefits to the mother and the baby, breastfeeding may reduce the mother's future risk of developing MS," she said.
The study was published in the journal Neurology.