Moderate
Exercise Decreases Risk of Breast Cancer
According to articles recently published in the Journal of
the American Medical Association and the International Journal
of Cancer, physical activity decreases the risk of developing
breast cancer in women.
Breast cancer claims the lives of approximately 40,000 women
annually in the United States alone, with over 200,000 diagnoses.
Since breast cancer is such a common malignancy, research
efforts have been focused on the discovery of risk factors
associated with an increased or decreased incidence of breast
cancer. Discovery of these associations may assist in helping
to prevent some women from developing breast cancer. Body
weight, diet and exercise have all been implicated in the
development of breast cancer, and researchers continue to
study these factors in association with breast cancer in order
to define their role.
Researchers affiliated with the Women's Health Initiative
Cohort Study evaluated the impact of physical activity on
the development of breast cancer in over 74,000 women. These
women were aged 50 to 79 years and were followed for at least
5 years. Among this group, 1,780 new cases of breast cancer
were diagnosed. An overall reduction of 14% in the risk of
developing breast cancer was noted in women who engaged in
physical activity, even those who only walked 1.25 to 2.5
hours per week. Longer duration of physical activity tended
to further decrease the risk of breast cancer; however, strenuous
activity was not necessary. Physical activity did not decrease
the risk of developing breast cancer in women who were obese.
1
The second study conducted by researchers in Finland evaluated
differences in breast cancer incidence in approximately 10,000
women who were physical education teachers or language teachers.
The two groups had a similar way of life except for physical
activity and were followed for 34 years. In the group of women
who taught physical education, there were 17% fewer cases
of breast cancer than those who were language teachers. The
reduction was greater for premenopausal cancers (21% less)
than for postmenopausal cancers (14% less). 2
Results from these two studies add to a growing list of studies
indicating that physical activity reduces the risk of the
development of breast cancer in women. Evidence is emerging
that strenuous activity is not necessary to obtain the benefits
in reducing this risk. Women who are not physically active,
particularly those at a high risk of developing breast cancer,
may wish to speak with their physician about beginning an
exercise program.
References:
1. McTiernan A, Kooperberg C, White E, et al. Recreational
Physical Activity and the Risk of Breast Cancer in Postmenopausal
Women. Journal of the American Medical Association.2003;290:1331-1336.
2. Rintala P, Pukkala E, Laara E, et al. Physical Activity
and Breast Cancer Risk Among Female Physical Education and
Language Teachers: A 34-year follow-up. International Journal
of Cancer. 2003;107:268-270.
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