Exercise Cuts Risk of Leukemia and Myeloma

You know that exercise is vital to health and well being, and physical activity is even helpful in preventing certain types of cancer. Until recently, however, leukemia and myeloma were not generally listed among those types for which you can cut your risk with exercise.

A study examined the question of exercise and risk reduction for various different types of cancer. The authors noted that a major strength of their study is that, to their knowledge, it is the largest study ever conducted on physical activity and cancer risk.

The researchers published their findings in the May 2016 issue of JAMA Internal Medicine. They noted the current state of affairs and the need for this study—physical activity reduces risks of heart disease, colon cancer, breast cancer, and endometrial cancers—but less is known about whether physical activity reduces the risk of other cancers, which actually represent about 75 percent of new cancer cases in the United States.

Exercise and Cancer Study - FAQs

How Common Is Physical Inactivity?

An estimated 51 percent of people in the United States and 31 percent of people worldwide do not get recommended levels of physical activity. Any decrease in risk of cancer associated with physical activity may therefore be relevant to public health and cancer prevention efforts.

What Is Leisure-Time Physical Activity?

Leisure-time physical activities were defined in this study as activities done at an individual’s discretion that improve or maintain fitness or health.

The research group included two categories of leisure-time activities: moderate intensity activities and other activities that have the vigorous intensity levels that are recommended by physical activity guidelines.

How Did Researchers Learn Which People Developed Cancer?

In this study they used questionnaires, but they also reviewed medical records and cancer registry databases. Overall, 99 percent of the cancer cases identified in the study were confirmed by medical records or pathology reports—the write-ups that pathologists do when analyzing a sample or biopsy specimen that turns out to be cancer.

How Many People Were in This Study?

This study drew from 1.44 million participants who had complete leisure-time physical activity data and no history of cancer at baseline.

More participants, 57 percent, were women, the median age at baseline was 59, and the median body mass index, or BMI was 26. Higher activity levels were associated with younger age, more education, lower BMI, and lower likelihood of being a current smoker.

How Many Cancer Types Were Studied?

The researchers looked at 26 different types of cancer. During a median of 11 years of follow-up, 186,932 cancers were identified.

What Were the Findings?

A higher versus a lower level of leisure-time physical activity was associated with lower risks for 13 of the 26 cancers studied.

Leisure-time physical activity was also associated with higher risk of malignant melanoma, and higher risk of non-advanced prostate cancer. A higher level of leisure-time physical activity was associated with a 7 percent lower risk of total cancer.

For myeloid leukemia and myeloma, this study found a strong inverse association—that is, more physical activity was strongly associated with less cancer—however, these findings were in contrast to a 2015 study that found no effect.

In this study, "myeloid" was defined by special codes, or ICD-0-3 histology types, and myeloid leukemias included: acute myeloid leukemia, chronic myeloid leukemia, and other myeloid/monocytic leukemia.

Other scientists have theorized that benefits from exercise in cancer risk reduction come from the associated weight loss—lose the fat, and you’ll cut your risk.

While that is certainly true of many diseases, this study’s findings suggested that physical activity and cancer associations were generally independent of body mass index, or BMI, which would argue against this fat hypothesis for most cancers.

Exercise, Diabetes, and Cancer Risk

For those struggling with overweight and obesity, one of the gems that can help is to know that even a little bit of weight loss can make a difference in terms of your risk profile, and here we are talking about your cardiovascular risk, and not necessarily your cancer risk.

The Diabetes Prevention Program study, or DPP study, showed that a 7 percent weight loss with intensive behavioral interventions could reduce the risk of developing type 2 diabetes by 58 percent. The DPP study was a landmark study where they showed that lifestyle really can change the development of diabetes.

When type 2 diabetes has been studied as a potential risk factor for the development of hematologic malignancies, or blood cancers, results have not generally been consistent.

Some studies have found an association between type 2 diabetes and the risk of developing lymphoma, leukemia, and myeloma. Such studies do not, however, explain how diabetes might increase a person’s risk.

For instance, obesity, diet, physical activity levels and glucose-lowering medications like metformin and other drugs are all things that tend to go with diabetes. So if a link were found with diabetes, you would also have to examine the factors that people with diabetes share to see what may be responsible for the increased risk.

According to research reported in the May 2012 issue of “Blood,” type 2 diabetes was associated with a mild-to-moderately increased risk of non-Hodgkin lymphoma, but not Hodgkin lymphoma. And, when non-Hodgkin lymphoma subtypes ware examined, the increased risk with type 2 diabetes was present for peripheral T-cell lymphoma, but not for other subtypes of non-Hodgkin lymphoma.

In most cases, researchers still don’t know what causes hematologic malignancies to develop. Certain infections such as Epstein-Barr virus, autoimmune disorders like rheumatoid arthritis, Sjögren’s syndrome, and systemic lupus erythematosus, or a positive family history may be important in the development of some of these cancers.

There is no conclusive evidence showing that type 2 diabetes is a strong risk factor for the development of hematologic malignancies, however.

Bottom Line

Even if this study on weight loss and cancer risk were completely off-base, and all of its findings spurious, light-to-moderate exercise would still be strongly recommended based on all of the other known health benefits, including general physical fitness and overall health and wellbeing.

Note that the present article pertains to the role of exercise in cancer prevention. The topic of exercise during cancer treatment is an entirely different topic.

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