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.