A review, update of physical activity guidelines for Americans

Tuesday, December 17, 2019

Any level of physical activity reduces the relative risk of some cancers by up to 20 percent, according to an interdisciplinary group of experts from the United States and Canada, confirming 2018 guidelines.

The group updated and confirmed findings on the relationship between physical activity and cancer risk presented in the 2018 Physical Activity Guidelines Advisory Committee Scientific Report, published by the American College of Sports Medicine (ACSM). The review was led by Anne McTiernan, a research professor in epidemiology at the University of Washington School of Public Health and full member at the Fred Hutchinson Cancer Research Center. She was also a member of the advisory committee that developed the 2018 guidelines.

The group reviewed 45 reports comprising hundreds of epidemiologic studies with several million study participants. They also conducted an updated systematic review of such reports and original research. Findings of the review were recently published in Medicine & Science in Sports & Exercise.

Researchers found strong evidence that physical activity reduces the risk of cancers of the breast, colon, endometrium, bladder, stomach, esophagus (adenocarcinoma) and kidney, as well as moderate evidence for an association with lung cancer risk. Relative risk decreased by about 10% to 20%. There was limited evidence that physical activity was associated with reduced risk for prostate cancer overall.

“While we discovered that many reports found a greater reduction in risk with increasing amounts of time exercised or higher intensity of exercise (i.e., a dose-response effect), we could not determine exact levels that provide given levels of effect,” McTiernan recently wrote in an ACSM blog post. “However, we found that almost any level of physical activity likely confers some benefit in reducing cancer risk.”

The researchers also found moderate or limited associations between greater amounts of physical activity and survival after diagnosis of breast, colorectal or prostate cancer. Preliminary results show relative risk reduced by about 40% to 50%.

McTiernan and others note there were several limitations to their work. The evidence relied on epidemiologic studies and, therefore, lacked any evidence from clinical trials in either preventing cancer or improving survival in persons with cancer. Additionally, the literature reviewed focused almost exclusively on aerobic activity and conclusions made in the 2018 report and updated review pertain only to this type of physical activity.

Co-authors are Christine Friedenreich, Peter Katzmarzyk, Kenneth Powell, Richard Macko, David Buchner, Linda Pescatello, Bonny Bloodgood, Bethany Tennant, Alison Vaux-Bjerke, Stephanie George, Richard Troiano and Katrina Piercy.