|
Exercise
May Lower Breast Cancer Risk
Participating in regular physical "recreational"
activity, even for just a few hours a week, may significantly
lower a woman's risk of developing early, localized breast
cancer, what doctors call breast carcinoma in situ (BCIS).
Dr. Leslie Bernstein of the University of Southern California
and colleagues compared the self-reported exercise habits
of 567 women diagnosed with BCIS with that of 616 "control"
women who did not have the disease. All of the women were
between the ages of 35 and 64.
In one-on-one interviews, the women provided information
about their lifetime involvement in activities such as walking,
jogging, bicycling, aerobics, swimming, sports, and dance.
The researchers calculated each woman's weekly average hours
and average energy spent exercising since she began menstruating.
After factoring out known breast cancer risk factors, such
as a history of cigarette smoking and use of hormone replacement
therapy, they found that overall the risk of BCIS was roughly
35 percent lower among women who reported "any"
physical activity compared to physically inactive women.
This level of reduced risk remained fairly constant with
increasing levels of activity.
However, when the investigators subdivided the women into
those with and without a family history of breast cancer,
they found no reduction in breast cancer risk among women
with a mother or sister with the disease.
"This is the first study of the impact of physical
activity on BCIS," Bernstein stated.
In a previous study, her team found a "strong protective
effect of lifelong exercise on the risk of invasive breast
cancer," she said. "For invasive disease, the
risk decreased proportionally with increasing level of exercise
and was restricted to women without a family history of
breast cancer."
In general, doctors are not exactly sure how physical activity
may guard against early breast cancer but they have several
theories. Exercise may lower levels of female hormones,
especially during adolescence. The known ability of exercise
to boost the immune system and make a person more sensitive
to insulin may also play a role.
"By identifying risk or protective factors for BCIS,
we have the opportunity to intervene a bit earlier in the
cancer process," Bernstein said.
SOURCE: Cancer, November 15, 2003 (published online October
6 at www.interscience.wiley.com/cancer)
Article Source: Reuters Health
Article Author: N/A
Net Reference 89
|
