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Studies of Women
Exercise improves cancer
survival, reduces risk, scientists say
Research demonstrates even moderate physical activity is a significant
factor in diminishing the risk or increasing the likelihood of survival
for certain cancers in women
March 29, 2004 -
Regular exercise, long associated with better cardiovascular health,
muscle tone and weight control, also may help prevent certain cancers
and improve the odds of cancer survival, according to studies released
today at the 95th Annual Meeting of the American Association
for Cancer Research.
Two studies report a
strong correlation between such ordinary activities as walking or
performing household chores and reduced risk of endometrial and breast
cancers, and between walking and improved rates of breast cancer
survival. Another demonstrates that moderate exercise decreased the
levels of a blood marker that predicts lower survival from several types
of cancer among high-risk, obese individuals.
Physical activity and endometrial cancer
risk:
Regular exercise, as
well as routine activities such as walking and household chores, may
reduce a woman's risk of endometrial cancer by as much as 30 to 40
percent, according to researchers from the Vanderbilt University Medical
Center in Nashville and the Shanghai Cancer Institute in China.
Charles E. Matthews,
Ph.D., of Vanderbilt, and his colleagues, evaluated 832 women with
endometrial cancer, aged 30 to 69 years, identified through the Shanghai
Cancer Registry. The control population, matched according to age, was
randomly selected from female residents of Shanghai. The women were
asked about the amount of walking and cycling for transportation,
intentional exercise and household activity in which they engaged as
adolescents – age 13 to 19 years – and as adults. Lifetime occupational
activity was also evaluated. Women who reported exercise participation
in both adolescence and adulthood were 30 to 40 percent less likely to
develop endometrial cancer than women who reported no exercise in either
life-period. Common activities, including household chores and daily
walking, were also found to reduce risk by about 30 percent. Reductions
in risk were evident for women who reported walking for 60 minutes each
day compared to women reporting less than 30 minutes of walking per day;
likewise for women who reported four or more hours per day of household
activity, compared to women reporting two hours or less each day.
Engaging in higher levels of overall physical activity appeared to
minimize some of the adverse effects of body weight on endometrial
cancer risk. Neither cycling nor occupational activity appeared to
influence endometrial cancer risk in this study.
"In recent years, we
have accumulated strong evidence that an active lifestyle can reduce the
risk of colon and breast cancer; now we are finding that physical
activity may also reduce risk of endometrial cancer" said Matthews, the
lead author of this report.
"We were particularly
pleased to see the beneficial effect on endometrial cancer risk of more
accessible and lower intensity forms of activity like walking for
transportation and doing household chores, as well as intentional
exercise," he added. "Our results support the idea that the risk of
cancer can be reduced by maintaining an active lifestyle."
Physical activity and survival after
breast cancer diagnosis: Abstract No. 1462
Researchers from
Brigham and Women's Hospital and Harvard University tested the
hypothesis that physical activity increases survival rates among women
with breast cancer.
"We already knew that
exercise improves the quality of life after a breast cancer diagnosis,"
said lead investigator Michelle D. Holmes, M.D., Dr.P.H., "but little is
known about how physical activity affects survival."
Holmes and her team
drew on participants in the Nurses' Health Study, reviewing data on
women with stages I, II, and III breast cancer, diagnosed between 1984
and 1996. In that study, leisure-time physical activity is measured in
metabolic equivalent task hours per week (met-hours/week – one met is
the energy expenditure and caloric requirement at rest. One hour of
walking represents three met-hours of physical activity.) The
researchers looked specifically at exercise beginning two years after
diagnosis, in order to avoid inclusion of women undergoing treatment.
The cohort of 2,296 women were followed from 1986 until either their
death from breast cancer or June 2002, whichever came first.
Taking into account the
stage of disease, obesity and other factors, the relative risk of death
from breast cancer was decreased with every level of physical activity
compared with being sedentary. The risk of death from breast cancer was
19 percent less among women who undertook 3-8.9 met-hours/week of
exercise; 54 percent less for 9-14.9 met-hours/week; 42 percent less for
15-23.9 met-hours/week; and 29 percent less for 24 or more
met-hours/week of recreational exercise.
"We were able to show
that even a moderate amount of physical activity improved the odds of
surviving breast cancer," Holmes said. "It is especially heartening for
women recovering from breast cancer to know that the benefit is as
readily accessible as walking for 30 minutes on most days of the week."
Effect of a yearlong exercise
intervention on markers of inflammatory response among postmenopausal
women: Abstract No. 5496
Another approach to the
association between exercise and cancer survival and prevention was
presented here today by researchers from the Fred Hutchinson Cancer
Research Center in Seattle, led by Cornelia M. Ulrich, PhD. C-reactive
protein (CRP) and serum amyloid A (SAA) are signals for inflammation
that have been associated with cancer risk and survival. Knowing that
these biomarkers often are elevated among the overweight, the team
investigated the effects of a moderately intense, yearlong exercise
program on CRP and SAA.
The study population
consisted of 114 postmenopausal, overweight (body mass index greater
than 24) and sedentary women, ages 50 to 75. About half of these
performed moderate physical activity 45 minutes per day, five days a
week, for one year, while the other half participated in weekly
stretching exercises. The concentrations of CRP and SAA in their blood
were measured at the beginning and the end of the test period.
"Among obese women,
those with a body mass index of 30 or higher," Ulrich reported,
"concentrations of CRP declined steadily over the course of the year
from a baseline of 0.40 milligrams per deciliter to 0.32 milligrams.
This effect of exercise on inflammatory markers may help to explain in
part the associations observed between increased physical activity and
reduced risk for cancer and other chronic disease."
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