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Physical activity associated with lower risks of 13 cancers

Leisure-time physical activity was associated with lower risks for 13 out of 26 cancers included in an investigation published in JAMA Internal Medicine.

Steven C. Moore, PhD, MPH, in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute, and colleagues stressed physicians should counsel inactive adults regarding the associations, regardless of body size or smoking history.

“To date, hundreds of prospective studies have examined associations between physical activity and cancer risk, but, owing to small case numbers, results have been inconclusive for most cancer types,” the researchers wrote. “Meta-analyses, to a degree, mitigate the sample size issue by pooling the published studies. However, pooled studies have typically been heterogeneous in study design (e.g., case-control vs. prospective cohort), physical activity types examined (e.g., leisure-time vs. occupational activity), and in the contrasts examined (tertiles vs. quintiles). Such heterogeneity can attenuate risk estimates, thereby masking true underlying associations.”

Steven C. Moore

Researchers used data from 12 prospective studies with U.S. and European cohorts of 1.44 million participants that self-reported physical activity.

Increased leisure-time physical activity was associated with a lower risk for the following 13 types of cancer: esophageal adenocarcinoma (HR = 0.58; 95% CI, 0.37-0.89); liver (HR = 0.73; 95% CI, 0.55-0.98); lung (HR = 0.74; 95% CI, 0.71-0.77); kidney (HR = 0.77; 95% CI, 0.70-0.85); gastric cardia (HR = 0.78; 95% CI, 0.64-0.95); endometrial (HR = 0.79; 95% CI, 0.68-0.92); myeloid leukemia (HR = 0.80; 95% CI, 0.70-0.92); myeloma (HR = 0.83; 95% CI, 0.72-0.95); colon (HR = 0.84; 95% CI, 0.77-0.91); head and neck (HR = 0.85; 95% CI, 0.78-0.93); rectal (HR = 0.87; 95% CI, 0.80-0.95); bladder (HR = 0.87; 95% CI, 0.82-0.92); and breast (HR = 0.90; 95% CI, 0.87-0.93). However, higher levels of leisure-time physical activity were also associated with an increased risk of prostate cancer (HR = 1.05; 95% CI, 1.03-1.08) and malignant melanoma (HR = 1.27; 95% CI, 1.16-1.40). After adjusting for BMI, researchers reported associations were lessened for esophageal adenocarcinoma and for cancers of the kidney, liver and gastric cardia, and were eliminated for endometrial cancer.

“Otherwise, the effects of adjustments for BMI were modest, and 10 of 13 inverse associations remained statistically significant after adjustment,” they wrote.

Overall, associations between leisure-time physical activity and cancer risks were similar between overweight or obese participants and normal-weight participants. In addition, smoking status changed the association for lung cancer, but not for other cancers related to smoking, the researchers noted.

"Our results confirm and extend the evidence for a benefit of physical activity on cancer risk and support its role as a key component of population-wide cancer prevention and control efforts," Moore told Healio Internal Medicine. "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 part of a healthy lifestyle and cancer prevention." – by Chelsea Frajerman Pardes

Disclosure: The researchers report no relevant financial disclosures.