If we needed more reason to go on a jog, or at least a brisk walk, a new study published in JAMA Internal Medicine offers some pretty strong incentive. It finds that people who get more activity in their leisure time have reduced risk of 13 types of the 26 types of cancer that were analyzed. The connections have largely been seen before, but this new analysis, in well over a million people, is a convincing once, since not only are the numbers are huge, but because the team breaks down the connection by type of cancer. And the size of some of the connections is striking.
Of the participants in the current study, gathered through the National Cancer Institute Cohort Consortium, 1.44 million provided information about the physical activity they did in their leisure time–walking, running, swimming and so on. Their average age was 59, and their average body mass index (BMI) was 26, meaning that many of the participants were overweight. No one had cancer at the time the study began. Over the next 11 years, give or take, about 187,000 incidents of cancer were logged.
Of the 26 types of cancer taken into account, there were links between getting more leisure time exercise and reduced risk of 13 varieties. People who were the most active (in the 90th percentile of activity level), as opposed to the least active (in the 10th percentile), had reduced risk of the following 13 types of cancer:
- Esophageal adenocarcinoma (42% lower risk)
- Liver (27% lower risk)
- Lung (26% lower risk)
- Kidney (23% lower risk)
- Gastric cardia (22% lower risk)
- Endometrial (21% lower risk)
- Myeloid leukemia (20% lower risk)
- Myeloma (17% lower risk)
- Colon (16% lower risk)
- Head and neck (15% lower risk)
- Rectal (13% lower risk)
- Bladder (13% lower risk)
- Breast (10% lower risk)
After body mass was taken into account, most of the connections still held. But certain kinds of cancer were dependent upon BMI as well–like esophageal adenocarcinoma, liver cancer, gastric cardio, kidney cancer and particularly endometrial cancer. These cancers are known to be linked to body fat (in particular to estradiol), so the finding that they were also linked in the current study isn’t so surprising. But the fact that other, non-BMI-related cancers were linked to exercise suggests, as have others before, that there are mechanisms beyond body fat that underlie the connection–like the effect of physical activity on immune function, inflammation and oxidative stress.
The types of cancer that did not seem to have a connection with exercise were non-Hodgkin lymphoma, thyroid, gastric noncardia, soft tissue, pancreas, lymphocytic leukemia, ovarian and brain.
And in the opposite direction, exercise was linked to an increased risk of prostate cancer (by about 5%), and malignant melanoma (27%). It’s not clear why the connection with prostate cancer would exist, since, as the authors write, “there is no known biologic rationale to explain this association." It could just be that more active men are getting screened for prostate cancer more frequently. But for melanoma it makes more sense, of course, since active people are more likely to spend time being active outside.
Clearly activity is good for us–and not just for weight loss, heart health or diabetes risk. It actually helps reduce the risk of a number of different cancers, and in some cases reduces them by a startling amount, underlining the fact that what we do every day may actually influence the "fate" of our health. You don’t have to take up sprinting or hit the gym every day, but getting in a healthy amount for you–and it’s generally a fairly personal determination–is a good idea. Exercise helps our bodies, and brains, in a number of different ways, and its connection with cancer risk is becoming clearer and clearer with each new study.
