“Although some risk factors for cancer—such as heritable genetic mutations—are difficult to control, others involve modifiable lifestyle factors that may help reduce the chances of developing the disease,” explains Steven C. Moore, PhD, MPH. “Prior studies on the association between physical activity and other cancers have yielded suggestive but not definitive results.”

Important New Data

For a study published in JAMA Internal Medicine, Dr. Moore and colleagues examined leisure-time physical activity in relation to the risk of 26 different cancer types. The authors examined data from a pooled analysis of 12 prospective cohort studies, which involved 1.44 million participants. “We initiated our large pooled study because we thought that we could confirm prior suggestive associations on the link between physical activity and cancer risk,” adds Dr. Moore.

When compared with people who had lower leisure-time physical activity levels, those with higher levels had a lower risk of 13 of the 26 cancers reviewed in the analysis. The risk of cancer was reduced by 20% or more for seven of the 13 cancers. “We replicated previous findings regarding this association for colon, breast, and endometrial cancers,” says Dr. Moore. “We also found lower risks for esophageal adenocarcinoma, myeloid leukemia, myeloma, and cancers of the liver, lung, kidney, gastric cardia, head and neck, rectum, and bladder. While we expected to identify new associations, we were surprised to identify as many as we did.”

According to Dr. Moore, the associations between physical activity levels and cancer risk were similar between overweight/obese and normal weight people. “Our data showed that 10 of the 13 inverse associations were independent of BMI,” he says. He adds that smoking status modified the association for lung cancer but not for other smoking-related cancers.

Significant Implications

Dr. Moore says the study results confirm and extend current evidence suggesting that there is a benefit of physical activity on cancer risk. “Our data support the role of physical activity as a key component of population-wide cancer prevention and control efforts,” he says. “Furthermore, our results support that these associations are broadly generalizable to different populations, including people who are overweight or obese and those with a history of smoking.”

The study notes that its primary strength is that it is among the largest ever conducted on physical activity and cancer risk, which allowed the authors to examine uncommon and rare oncologic disease that together constitute most incident cancers. However, Dr. Moore says more research can further support findings of the study. “Future studies should target the type, intensity, and amount of physical activity in greater detail that is needed to reduce overall cancer risk in subsets of people,” he says.

Steven C. Moore, PhD, MPH, has indicated to Physician’s Weekly that he has no financial disclosures to report.