Here's another reason to get active: Exercise may
reduce the risk of 13 types of cancer, a new study finds.
Researchers analyzed information from 1.4 million
people in the United States and Europe; the subjects were in 12 different study
groups and were followed for about 11 years. Participants were asked whether
they did moderate or vigorous exercise in their free time, like walking,
swimming or running, and how much physical activity they got.
During the study period, more than 186,000 cases
of cancer were diagnosed in the study participants.
People were classified as doing higher levels of
exercise if they were in the top 10 percent of all people in their study groups
for the amount of exercise they did. These individuals had a reduced risk of 13
types of cancer compared to the people who were in the lowest 10 percent of
their study groups.
These were the 13 cancers, with their associated
amounts of risk reduction:
Esophageal cancer, a 42 percent lower risk
Liver
cancer, a 27 percent lower risk
Lung
cancer, a 26 percent lower risk
Kidney
cancer, a 23 percent lower risk
Stomach
cancer of the cardia (top portion of the stomach), a 22 percent lower risk
Endometrial cancer, a 21 percent lower risk
Myeloid
leukemia, a 20 percent lower risk
Myeloma, a 17 percent lower risk
Colon
cancer, a 16 percent lower risk
Head
and neck cancer, a 15 percent lower risk
Rectal
cancer, a 13 percent lower risk
Bladder
cancer, a 13 percent lower risk
Breast
cancer, a 10 percent lower risk
Overall, high levels of physical activity were
linked with a 7 percent lower risk of any cancer, according to the study.
"These findings support promoting physical
activity as a key component of population-wide cancer-prevention and -control
efforts," the researchers wrote in the May 16 issue of the journal JAMA
Internal Medicine.
For most of the cancers (10 out of 13), exercise
reduced the risk of the disease regardless of people's body mass index or
smoking habits. [4 Easy Ways to Get More Exercise]
Interestingly, high levels of physical activity
were actually linked with a slightly higher risk of prostate cancer (5 percent
increased risk). A biological reason for this finding is not known, and it's
possible that physically active men are more likely to get screened for
prostate cancer, which would lead to more cancers identified in this group, the
researchers said.
But high levels of exercise were also linked with
a 27 percent higher risk of malignant melanoma, which is likely the result of
more sun exposure, the researchers said. Efforts to prevent cancer that focus
on exercise should also emphasize how people can protect themselves from sun
exposure when they exercise outdoors, the researchers said.
The new findings "underscore the importance
of leisure-time physical activity as a potential risk-reduction strategy to
decrease the cancer burden in the United States and abroad," Marilie
Gammon, of the University of North Carolina at Chapel Hill, and colleagues
wrote in a commentary accompanying the study.
However, the new study did not look at exactly
how much exercise is needed, how intense the exercise should be or when in life
people should start exercising to get these benefits, so those questions should
be the focus of future research, the commentary said.
More research is also needed to determine exactly
how exercise lowers the risk of cancer, the commentary said. Understanding the
underlying mechanisms for the link could help identify potential targets for
cancer prevention, the authors said
.
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