Exercise Linked to Lower Risk of Certain Types of Cancer

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A new study published in JAMA Internal Medicine offers another strong incentive to go for a run, or at least a brisk walk. It finds that people who get more activity in their leisure time have a reduced risk of 13 types of the 26 types of cancer that were analyzed.

The connections have largely been seen before, but this new analysis, drawn from well over a million people, is a convincing one, since not only are the numbers of the study participants huge, but because the research team breaks down the connection by type of cancer. And the magnitude of some of the connections is striking.

The data are based on 12 previous studies involving a total 1.44 million people. The results include a 42% lower risk of esophageal cancer, 27% lower risk of liver cancer, 26% lower risk of lung cancer and a 23% lower risk of kidney cancer.

Even after adjusting for body weight, Dr. Steven C. Moore of the National Institutes of Health in Rockville, MD, 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% increased risk of malignant melanoma, however, and a slightly increased (5%) 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.

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. 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. 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 clusters of healthy behaviors. It’s hard to know which healthy behavior it is (that leads to risk reduction),” said Dr. Gammon.

Monday, May 23, 2016 / Vol. 24 / No. 20