Physical Activity Reduces Risk of 13 Types of Cancer

High levels of physical activity are associated with lower rates of cancer, according to a new study published in JAMA Internal Medicine.

Researchers from the National Cancer Institute, the National Institutes of Health, and the American Cancer Society pooled data from 12 prospective cohorts of self-reported physical activity from both the US and Europe to determine how leisure-time physical activity related to incidence of cancer, and whether or not there are associations with body size and smoking.

The sample contained 1.44 million adults between the ages of 19 and 98 years and included 26 types of cancer. Participants were followed for approximately 11 years, during which about 187,000 cases of cancer occurred. Leisure-time physical activity was defined as activities done at an individual’s discretion that improve or maintain fitness or health. Activity of moderate intensity was set at 3+ metabolic equivalents (METs) and vigorous was set at 6+ METs.

“Leisure-time physical activity is known to reduce risks of heart disease and risk of death from all causes, and our study demonstrates that it is also associated with lower risks of many types of cancer,” Steven C. Moore, PhD, of the National Cancer Institute, said in a statement. “Furthermore, our results support that these associations are broadly generalizable to different populations, including people who are overweight or obese, or those with a history of smoking. Health care professionals counseling inactive adults should promote physical activity as a component of a healthy lifestyle and cancer prevention.”

The researchers noted that high levels of physical activity were associated with reduced risk for 13 types of cancer with risk reduction of 20% or more for 7 of these, and a 7% drop in total cancer. Leisure-time physical activity was associated with higher risks of malignant melanoma and prostate cancer. Associations proved generally similar between overweight/obese individuals and those at a normal weight. Smoking status modified the association for lung cancer, but not other smoking-related cancers.

Prior research has shown that physical activity reduces levels of cancer-related biomarkers; this led to the hypothesis that exercise reduces the risk of cancer but because associations remained statistically significant when accounting for BMI, this appears to be disproven. Only for cancers that are known to be obesity related, was BMI considered a mediating factor.

Leisure-time physical activity was strongly inversely associated with lung cancer and unassociated with endometrial cancer for those whose BMI was under 25.

Overall, this study differs from previous surveys because its pool is more expansive. The results also suggest physical activity may be associated with a lower risk of a wider breadth of types of cancer than previously described, and they bolster the evidence for associations that were previously only weakly supported.

“For years, we’ve had substantial evidence supporting a role for physical activity in three leading cancers: colon, breast, and endometrial cancers, which together account for nearly one in four cancers in the United States,” said co-author Alpa V. Patel, PhD, from the American Cancer Society. “This study linking physical activity to 10 additional cancers shows its impact may be even more relevant, and that physical activity has far reaching value for cancer prevention.”