Physical activity associated with lower risk of many cancers

NIH | MAY 28, 2016

Leisure-time physical activity has many health benefits. In addition to a reduced risk for heart disease, increased physical activity has been associated with a lower risk for colon, breast, and endometrial cancers.

Physical activity. Image credit: www.localfitness.com.au/Wikimedia commons (CC BY-SA 3.0)

An international team examined the associations between physical activity and various cancers. The researchers pooled data from 12 studies that together followed a total of 1.44 million people over time. Study participants were 19 to 98 years old, from the United States and Europe, 57% female, and had no history of cancer. The studies assessed physical activity by using surveys that asked about time spent in moderate to vigorous leisure-time physical activities, such as walking, running, or swimming.

Participants were followed for a median of 11 years. During this time, 187,000 new cases of cancer arose. Cancer types were selected for analysis if there were at least 300 cases.

The researchers found that people with the highest level of leisure-time physical activity had a reduced risk for 13 of 26 types of cancer compared to those with the lowest level of activity. People with the highest activity had a 20% lower risk for 7 cancer types: esophageal adenocarcinoma, liver, lung, kidney, gastric cardia, endometrial, and myeloid leukemia. They also had a 10-20% lower risk for myeloma and cancers of the head and neck, rectum, bladder, and breast.

The scientists controlled for factors such as age, sex, smoking status, alcohol use, diet, education, race/ethnicity, and body mass index (BMI). Ten of the 13 associations remained after adjusting for BMI. This suggests that, for the majority of cancers, physical activity reduces risk through mechanisms other than lowering body weight.

Leisure-time physical activity was associated with a greater risk of malignant melanoma, particularly in people from regions with strong sunlight. Outdoor physical activity increases sun exposure, which may lead to the higher melanoma risk. The investigators also found an association between physical activity and a higher risk of prostate cancer. There is no known biological rationale for this finding. Men who are more physically active might be more likely to get screened for prostate cancer, thus increasing rates of detection.

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