Boston: Weight gain after the menopause may mean an increased risk of breast cancer, according to a new US study.

Researchers at the Brigham Women’s Hospital and Harvard Medical School, Boston, examined the links between weight gain and the risk of breast cancer among post-menopausal women. They discovered that weightloss after the menopause lowers levels of circulating oestrogen, the hormone that elevates cancer risk, in women. It has already been proven that weight gain in earlier life also raises cancer risk.

The researchers examined changes in weight in two different life periods – after the age of 18 and after menopause over a follow up period of 24 years. The study involved a total of 87, 143 postmenopausal women, aged 30 to 55 years, who were followed up for up to 26 years to analyse weight change since age 18. Weight change since menopause was assessed among 49,514 women. The study is published in the Journal of the American Medical Association.

Women who gained about 55 pounds or more since age 18 were at a 45 percent increased risk of breast cancer, compared with those who maintained their weight, with a stronger association among women who have never taken postmenopausal hormones.
Women who gained about 22 pounds or more since menopause were at an 18 percent increased risk of breast cancer. Those who lost about 22 pounds or more since menopause (and kept the weight off) and had never used postmenopausal hormones were at a 57 percent lower risk of breast cancer than those who simply maintained their weight. The researchers concluded that 15 percent of the study’s breast cancer cases may be attributable to weight gain of 4.4 pounds or more since age 18 and 4.4 percent of the cases may be attributable to weight gain of 4.4 pounds or more since menopause.