(Ivanhoe Newswire) -- Type 2 diabetes mellitus affects nearly 9 million adult women in the United States. New research, however, may help lower that number. According to a recent study, women who breastfeed longer have a decreased risk of developing type 2 diabetes.

Alison M. Stuebe, M.D., from Brigham and Women's Hospital and Harvard Medical School in Boston, and colleagues studied the association between lactation duration and development of type 2 diabetes. Researchers compared data on 83,585 women already gave birth and participated in the Nurses' Health Study (NHS) to data on 73,418 women involved in the Nurses' Health Study II (NHS II).

Investigators found 5,145 cases of type 2 diabetes diagnosed during NHS and 1,132 cases diagnosed during NHS II. The research was restricted to women who reported a birth in the past 15 years with a control for body mass index and other risk factors related to type 2 diabetes. The study revealed a 15 percent reduced risk of diabetes in the NHS and a 14 percent reduced risk in the NHS II per additional year of breastfeeding. Among women who reported their last birth more than 15 years ago, there was no association between duration of lactation and type 2 diabetes.

Dr. Stuebe says, "Increased duration of breastfeeding was associated with reduced risk of type 2 diabetes in two large cohorts of women. Together with clinical evidence of improved glucose homeostasis in lactating women, these data suggest that lactation may reduce the risk of type 2 diabetes in young and middle-aged women."

SOURCE: The Journal of American Medical Associaton, 2005; 294:2601-2610