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 Based on data from 12 previous studies involving a total 1.44
million people, researchers found that with few exceptions, high
versus low amounts of moderate to vigorous activity meant lowered
risk for 13 out of 26 types of cancer.
The results include a 42 percent lower risk of esophageal cancer, 27
percent lower risk of liver cancer, 26 percent lower risk of lung
cancer and a 23 percent lower risk of kidney cancer.
Even after adjusting for body weight, Dr. Steven C. Moore of the
National Institutes of Health in Rockville, Maryland, and his
colleagues found lowered risk for 10 of the 13 cancers with higher
levels of leisure-time physical activity. After factoring in
smoking, they found it only affected the risk of lung cancer, but
not other smoking-associated cancers.
Higher levels of activity were tied to a 27 percent increased risk
of malignant melanoma, however, and a slightly increased (5 percent)
rise in prostate cancer risk.
“Our results support that these associations are broadly
generalizable to different populations, including overweight or
obese individuals, or those with a history of smoking. These
findings support promoting physical activity as a key component of
population-wide cancer prevention and control efforts,” the
researchers conclude in JAMA Internal Medicine.
Dr. Moore did not respond to a request for comment.
The study team looked at physical activity levels across the various
studies in terms of Metabolic Equivalents of Task, or METs,
representing the amount of energy expended per minute in a specific
activity. For example, resting expends 1 MET per minute, moderate
activity like walking uses 3 to 5.9 METs and vigorous exercise like
running uses more than 6 METs.
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The studies included in the analysis asked participants about
specific activities like walking, running or swimming, or they
quantified overall weekly participation in moderate and vigorous
activities. The middle-ground for most participants worked out to
eight METs per hour per week, or about 150 minutes of moderate
activity like walking.
The design of this analysis is "probably one of the strongest ... we
could have," said Dr. Marilie D. Gammon, of the University of North
Carolina, Chapel Hill, senior author of a commentary accompanying
the study.
“The study authors also looked at a lot of rare tumors. In some ways
they were able to confirm what we’ve seen in the more common tumors,
but they also report on tumors that have been much harder to nail
down. I think this is good news, especially when it comes to the
rare tumor types. It gives us hope that (physical activity) could be
an important public health strategy for risk reduction.”
What’s needed now is more research to determine what mechanisms are
involved in risk reduction, she added. “Physical activity is just
one of the cluster of healthy behaviors. It’s hard to know which
healthy behavior it is (that leads to risk reduction).”
SOURCE: http://bit.ly/1qnrIaN and http://bit.ly/1V611UR JAMA
Internal Medicine, online May 16, 2016.
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