1. This multinational cohort study showed that leisure time activity was associated with lower cancer risk in 13 adult cancers.
2. Physical activity was associated with a higher risk of malignant melanoma and prostate cancer.
Evidence Rating Level: 2 (Good)
Study Rundown: It is well known that physical activity lowers one’s cardiovascular risk, however less is understood about the potential association of exercise and cancer risk. This cohort study aimed to determine the association of leisure-time physical activity with the incidence of common cancers.
Higher leisure-time physical activity was associated with lower risk of 13 cancers: esophageal adenocarcinoma, liver, lung, kidney, gastric cardia, endometrial, myeloid leukemia, myeloma, colon, head & neck, rectal, bladder and breast. After adjustment for body mass index (BMI), 10 of the 13 associations remained statistically significant. Interestingly, leisure-time physical activity was associated with higher risk of malignant melanoma and prostate cancer. Results after adjustment for BMI remained robust. Smoking modified the association between exercise and lung cancer but not for other smoking-related cancers. Strengths of this study included its multinational, large population cohort. Limitations included the self-reported measure of exercise, which may have biased the results. Also, physical activity in the top and bottom tenth percentile were compared, rather than examining it as a continuous variable.
In-Depth [prospective cohort study]: This study was conducted using 12 prospectively gathered American and European cohorts collected between 1984 and 2004. Leisure-time physical activity was defined as activity done at an individual’s discretion that improve or maintain health and were ascertained by self-reported questionnaires. There were no specifics defining the exercise intensity. Cancers were ascertained also with self-reported questionnaires and review of medical records. Multivariable Cox regression was used to estimate hazard ratios.
A pooled total of 1.44 million participants were included in this study as they were able to provide leisure-time physical activity data and had no cancer at baseline. Higher levels of physical activity were significantly associated with lower cancer rates in 13 of 26 studied cancers: 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 084; 95%CI 0.77-0.91), head & 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). Cancer risk was increased with increased physical activity in prostate (HR 1.05; 95%CI 1.03-1.08) and malignant melanoma (HR 1.27; 95%CI 1.16-1.40).
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