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Active Lifestyle Reduces Risk of Invasive Breast Cancer
Researchers Say It’s Never Too Late to Start Exercising
(PHILADELPHIA Feb 2007) -- Six or more hours per week of strenuous
recreational activity may reduce the risks of invasive breast cancer by
23 percent, according to researchers from the University of Wisconsin
Paul P. Carbone Comprehensive Cancer Center (UWCCC). Their report in the
February issue of Cancer Epidemiology Biomarkers & Prevention, based on
a survey of over 15,000 women, shows that exercise has a protective
effect against invasive breast cancer throughout a woman’s lifetime.
The results provide further evidence that for most women physical
activity may reduce the risk of invasive breast cancer, the researchers
To gain further insights into the mechanisms of risk reduction for
breast cancer, the researchers investigated the relationship between
physical activity and breast cancer risk in a population-based case
control study in Massachusetts, New Hampshire, and Wisconsin.
During structured telephone interviews, the researchers questioned 7,630
women without breast cancer, 1,689 survivors of in situ, or
non-invasive, breast cancer and 6,391 survivors of invasive breast
cancer, all between the ages of 20 and 69. They asked detailed questions
about physical activity, occupation, family history of breast cancer,
menopausal status, and body mass index.
According to the researchers, women who exercised had a reduced risk of
developing invasive breast cancer provided they didn’t have a family
history of breast cancer. This reduction in risk was apparent whether
the physical activity took place early in life, in the postmenopausal
years, or in the recent past.
“A woman's hormone levels naturally fluctuate throughout her life, and
we have found that exercise likely offers protection against breast
cancer regardless of a woman's stage in life,” said Brian Sprague, a
UWCCC research assistant and lead author of the study. “The take-home
message for women should be that it is never too late to begin
Previous research has linked high levels of estrogen to an increased
risk for developing breast cancer. Women who exercise heavily are, in
general, older at the time of the first period, and tend to have
irregular periods and a shortened estrogen-producing phase, which
translates in a lower body exposure to estrogen, the researchers say.
Similarly, postmenopausal women who are physically active have also been
shown to have lower levels of estrogen. This reduction may explain why
increased physical activity reduces the risk of breast cancer, according
to Amy Trentham-Dietz assistant professor at the University of
Wisconsin-Madison and member of the University of Wisconsin Paul P.
Carbone Comprehensive Cancer Center. Other potential mechanisms include
prevention of weight gain, regulation of insulin sensitivity and
alterations in immune function.
Taking all these factors into consideration, “intervention studies
assessing the effect of physical activity on estrogen and other hormone
exposure, and other biomarkers of risk would provide valuable insights
on the mechanisms of physical activity in reducing breast cancer risk,”
“Further studies of population subgroups are necessary to gain a better
understanding of the relation of physical activity to breast cancer
risk, and to identify the groups most likely to gain benefit from it,”
said Trentham-Dietz. “Future research should also consider household
activity in addition to recreational and occupational activities.”
Source: American Association for Cancer Research
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