Anne McTiernan, MD, PhD, FACSM |
Worldwide, more than 18 million people develop a new cancer each year, and more than 9.5 million die of the disease. There is increasing evidence that a physically active lifestyle reduces the risk of developing several types of cancer and may also promote longer survival in people living with cancer.
In 2018, the U.S. Physical Activity Guidelines Advisory Committee reviewed the state of science on physical activity and cancer in human population studies. After considering data from 45 systematic reviews, meta-analyses and pooled analyses, as well as original reports, the Committee found strong evidence that regular physical activity significantly reduces risk of bladder, breast, colon, endometrial, esophageal adenocarcinoma, kidney and stomach cancers. The relative risk reduction ranged from 10 to 20 percent for those who engaged in the highest versus lowest levels of activity. The committee found moderate or lower evidence that risk of other cancers was also reduced with physical activity.
Recently, we published a manuscript in Medicine & Science in Sports & Exercise that updated and confirmed the Committee findings. The Committee also investigated what levels of physical activity give optimal protection against cancer. While we discovered that many reports found a greater reduction in risk with increasing amount 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. However, we found that almost any level of physical activity likely confers some benefit in reducing cancer risk. Since the epidemiologic literature we reviewed focused almost exclusively on aerobic activity, the Committee’s conclusions pertain only to this type of physical activity.
The effects of physical activity on reducing cancer risk were seen in both women and men, although the magnitude of the relationships varied by sex for some cancers. The evidence suggested that physical activity protects against cancer in diverse race/ethnic groups, but data were limited for Blacks and Asians, and sparse for Latino, Native American and Pacific Islander populations. For some cancers, the role of physical activity on cancer risk was more pronounced in persons of normal weight compared to those with obesity.
The Committee also investigated whether physical activity can prolong survival or reduce recurrence and new cancers among those living with cancer. We concluded that there was moderate or limited evidence that high levels of physical activity reduce risk of deaths in persons living with breast, colorectal or prostate cancers.
The Committee identified future research needs, including epidemiologic studies of the associations of physical activity on risk for less common cancers; more studies in diverse age, racial, ethnic and socioeconomic groups; investigations of dose-response relationships; identifying ideal levels of activity for protecting against cancer; and studies of diverse types of physical activity. We identified need for randomized controlled clinical trials testing effects of different types and doses of exercise on cancer biomarkers and on prognosis in persons with cancer. Given the increasing length of survival in many cancers, the Committee also identified need for long-term follow-up of cancer survivors to determine effects of exercise on cancer progression and mortality.
While a physically active lifestyle reduces risk for several cancers, some recreational and professional sports may increase exposure to cancer-causing agents. Examples include unprotected sun exposure, talcum powder products, air pollution, smokeless tobacco, some muscle-building products, some synthetic turf materials and alcohol use. Individuals should avoid these potential carcinogens as much as possible; there are no data on whether physical activity can attenuate the effects of these carcinogens on risk for specific cancers.
Recently, an ACSM roundtable came to similar conclusions as did our Committee, and importantly, developed guidelines for clinicians to ensure that cancer patients and survivors benefit from physical activity to improve their health and quality of life. The roundtable concluded that exercise testing and training were generally safe for cancer survivors, and that survivors should avoid inactivity. It stated that specific doses of aerobic, resistance and combined exercise programs could help with common cancer-related health outcomes including symptoms of anxiety, depression and fatigue, and could improve physical functioning and health-related quality of life. The guidelines follow the ACSM Exercise is Medicine approach, and recommend that oncology clinicians: assess, advise, and refer cancer survivors to exercise. ACSM provides a service to oncologists and survivors with an online directory of exercise specialists who work with cancer survivors.
In summary, the 2018 U.S. Physical Activity Guidelines Advisory Committee identified the critical role of physical activity in reducing risk for cancer and for improving prognosis in persons living with cancer. ACSM provides leadership and support to promoting physical activity for all persons and can extend the Exercise is Medicine model to preventing and treating cancer.
Learn more about the Physical Activity Guidelines for Americans, 2nd Edition
Anne McTiernan, MD, PhD, FACSM, is an Internist and Epidemiologist, and is a Member of the Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, and Research Professor, Schools of Public Health and Medicine, University of Washington, Seattle, Washington. Her research focuses on physical activity, diet, obesity and risk for cancer development and prognosis. Dr. McTiernan served on the 2008 and 2018 U.S. Physical Activity Guidelines Advisory Committees. Dr. McTiernan presented the Joseph B. Wolffe Memorial Lecture at the 2018 ACSM Annual Meeting.