But, exercise helps prevent the disease, two additional studies report,,,,
TUESDAY, May 13 (HealthDay News) -- New research has found both bad news and good news on breast cancer risk.
The bad news is a risk factor you can't change: Women whose sisters were diagnosed with breast cancer face an increased risk of breast cancer throughout their lives, regardless of their sister's age at diagnosis, according to a study in the May 13 issue of the Journal of the National Cancer Institute (JNCI).
The good news comes from a risk factor you can do something about: Women who exercise are much less likely to develop breast cancer, according to two new research studies -- one from the same issue of JNCI, and the other from the 2008 online first edition of the British Journal of Sports Medicine.
The first study from JNCI compared the rate of breast cancer in nearly 24,000 sisters of women with breast cancer to the rate of cancer in nearly 1.8 million women with sisters who didn't have breast cancer. All of the women were from Sweden, and the data collection for the study spanned from 1958 to 2001.
The researchers found that women between the ages of 20 and 39 who had a sister who'd been diagnosed with breast cancer faced a sixfold higher risk of breast cancer than did women whose sisters didn't have breast cancer. The excess risk declined as the women aged but didn't disappear. Women who were older than 50 with a sister with breast cancer had about a twofold risk of developing the disease, according to the study. And, it didn't matter what age the sister was when she was diagnosed.
"After the diagnosis of breast cancer in a family, the other sisters -- especially the youngest -- have an increased risk of breast cancer that persists for 20 years," said one of the study's authors, Marie Reilly, a professor of biostatistics at the Karolinska Institute in Stockholm, Sweden. "T
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