Breastfeeding for more than 6 months can delay the onset of breast cancer by 10 years

(http://www.theguardian.com) A study performed at the University of Granada in Spain shows evidence that women who breastfeed for over six months and don't smoke can delay the onset of breast cancer by 10 years. The study was published online on August 13, 2013, in the Journal of Clinical Nursing.

The study involved 504 females between the ages of 19 and 91 who were diagnosed with breast cancer at the San Cecilio University Hospital in Granada. As stated in the abstract, the purpose of the study was "[t]o evaluate at what age parous and nonparous women were diagnosed with breast cancer. Factors taken into account for parous women were whether they had breastfed their children, and if so, the length of the lactation period. Other factors considered for both groups were obesity, family histories of cancer, smoking habits and alcohol consumption."

The researchers analyzed the medical records of their subjects, noting various factors such as when each woman was diagnosed with breast cancer, if and how long they breastfed, and their smoking habits. The researchers then compiled this information into a "conditional inference tree" to see how the various factors relate to one another.

The average breast cancer diagnosis age for women who breastfed for at least six months and didn't smoke was 68.4 years old. Women who neither smoked nor breastfed were diagnosed at an average of 58 years.The authors say that a woman's risk of breast cancer is reduced by 4.3% for each year she breastfeeds. "Based on these findings, the incidence of this disease could be reduced from 6.3% to 2.7% if women breastfed their children for more than six months," the authors say.

As per the abstract, the "study concluded that breastfeeding for over six months not only provides children with numerous health benefits, but also protects mothers from breast cancer when the mothers are nonsmokers."

Breastfeeding and pregnancy are thought to protect against breast cancer by reducing oestregen levels. This claim is supported by the new study.