Walking, Running Reduce Risk Of Death From Brain Cancer

Every year, in the United States alone, about 25 thousand people are diagnosed with primary cancers of the brain or central nervous system, cancers that originate in the central nervous system. Another 200,000 people are diagnosed with brain cancers that originated outside the brain and central nervous system.

About 70% of brain cancers are glioblastomas, metastatic tumors that arise in glial cells, cells that "glue" neurons in the brain together to form organized tissues. Cancerous tumors of the pituitary, the "master gland" of the endocrine system, located in the brain, and of the 

Tall people are more likely to develop brain cancers than people of short stature or normal height. Men are more likely than women to develop gliomas, and women are more likely than men to develop other kinds of cancerous brain tumors such as pituitary adenomas and hemangiomas. tumors that develop in the linings of blood vessels in the brain.

The only certain controllable risk factor for glioma is exposure to ionizing radiation. Ironically, exposing the brain to multiple imaging procedures may increase the risk of developing a brain tumor. On the other hand, some factors seem to protect against the development of brain tumors.

What Might Reduce Your Risk of Brain Cancer?

Scientists have been looking for lifestyle choices that might reduce the risk of brain cancer for several decades. The Million Woman Study, conducted in the UK, and the European Prospective Investigation into Cancer and Nutrition, conducted in continental Europe, failed to find a significant protective effect of exercise against the development of cancerous brain tumors. 

In the United States, the The National Institutes of Health–American Association of Retired Persons study tracked more than 300,000 subjects and discovered a 35% lower risk of glioma for participants who could remember getting regular exercise when they were between 15 and 18 years old, but the study failed to find protection from getting exercise later in life. 

The US National Walkers' and Runners' Health Study recruited participants who not only exercised by walking or running on a regular basis, but who could provide data on how much they exercised, and how vigorously. Participants in the study could describe how far they ran or walked, not just for how much time they ran or walked. This selection factor was critical for the usefulness of the data collected in the study, because the inability to recall exercise routes would have biased the results toward the "null," no-effect interpretation of the data.

See Also: Brain Cancer - Treatment Alternatives

The reported the usual miles run per week, and the walkers reported the usual miles walked per week and their usual pace in minutes per mile. The researchers used these data to calculate METs, where 1 MET is the amount of energy usually expended while doing no exercise at all. The volunteers were asked question about lifestyle, weight, height, and diet, and then the researchers monitored the National Death Registry for an average of 11+ years for deaths from brain cancer.

How Much Exercise Is Enough to Protect Against Brain Cancer?

Of the 153,240 walkers and runners enrolled in the study in the 1990's, just 110 died of brain cancer, from 8 to 15 years after the researchers began tracking them. Even with this relatively small number of deaths, unlike earlier studies, the National Walkers' and Runner's Health Study found some clear trends in the risk of death from brain cancer.

• The risk of brain cancer was 43.2% lower among participants who got between 1.8 and 3.6 MET hours of exercise per day.
• The risk of brain caner was 39.8% lower among participants who got more than 3.6 MET hours of exercise per day.

How much exercise is that?

• 1.8 MET hours is roughly equivalent to walking 2 miles an hour (3 km per hour) for 1 hour.
• 1.8 MET hours is roughly equivalent to walking 3 miles an hour (5 km per hour) for 40 minutes.
• Playing tennis for 10 minutes burns 2 METs of energy.
• Swimming for 15 minutes burns 2 METs of energy.
• Running at 13 miles per hour (20 kilometers per hour) burns 3.6 MET of energy in 15 minutes.

More is not necessarily better, but getting lots of exercise is also protective.

The study also found that brain cancer deaths were over 4 times as common among whites as non-whites. For reasons not explained, people born during the winter are more likely to develop brain cancer. Taking diabetes medications seems to protect against brain cancer, while having to take high blood pressure medication seems to increase the risk.

Perhaps the most significant interaction, however, was between exercise, age, and survival time.

In people who have not yet reached the age of 50, gliomas often take the form of astrocytomas, slow growing cancers that may allow survival for 5 to even 15 years. 

In older persons who have gliomas that are not the slower-growing astrocytomas, there is considerably evidence that exercise really makes a clear but limited difference in survival time. It may be that in people under the age of 50 gliomas progress so slowly that researchers simply have not been able to measure the benefits of exercise, yet. 

See Also: Walking Away From Cancer

Researchers caution that correlation is not the same as causation. They don't really know whether exercise protects against death from brain cancer or that people who are already resistant to brain cancer are just more likely to exercise. But since exercise also helps brain cancer patients maintain quality of life longer, getting that daily run, or daily walk, as long as possible is probably a good idea. And making a habit of getting exercise beginning as early in life as possible may extend life in ways that we stay too healthy to appreciate.