ATLANTA -- The amount of weight a woman gains after age 18 is a strong indicator of how likely she is to get breast cancer later in life, according to new research released yesterday by the American Cancer Society.
In one of the largest studies of weight and breast cancer to date, researchers said older women who gained 20 to 30 pounds after high school graduation were 40 percent more likely to get breast cancer than women who did not.
The risk doubled if a woman gained more than 70 pounds, said Heather Spencer Feigelson, senior epidemiologist with the American Cancer Society.
"Breast cancer is strongly dependent on body weight," Feigelson said. "Even modest amounts of weight gain lead to a significantly increased risk of breast cancer." Weight gain has long been known to be a risk factor for breast cancer.
The society estimates that excess weight contributes to between one-third and one-half of all breast cancer deaths in older women.
But the cancer society researchers wanted to examine more specifically the link between breast cancer and the amount of weight gained, and this was the first in such a large group.
The study included 1,934 breast cancer cases among 62,756 women involved in a separate long-term cancer prevention study. Postmenopausal women ages 50 to 74 were asked their weight when the study began in 1992 and their weight when they were 18 years old. Surveys were sent to the women in 1997, 1999, and 2001 to inquire about any new occurrences of cancer.