Running and walking reduce the likelihood of your developing a brain tumour. Walking for 36-72 minutes every day or jogging for 15-30 minutes gives optimal protection. Bio-statistician Paul Williams at Ernest Orlando Lawrence Berkeley National Laboratory discovered this after following 150,000 runners and walkers for over ten years.
Williams has devoted his work to the National Runners’ and Walkers’ Health Studies, a large-scale epidemiological project which contains data on 111,266 runners and 42,136 walkers, and continues to publish study after study. In previous years Williams has shown that running can reduce the chance of wear and tear on joints – at least if you are not overweight, and that runners put on weight if they start to run less.
In May 2014 Williams published the results of a study in Medicine & Science in Sports & Exercise, in which he examined the relationship between running, walking and brain cancer. Brain cancer is relatively rare, and scientists know little about the lifestyle factors that can protect against it.
Williams expressed the participants’ physical activity in MET-hours per day. Scientists say that we need to get in 1.8 MET-hours a day. That’s the equivalent of 36 minutes of walking or 15 minutes of jogging.
The runners and walkers that managed to do 1.8 MET-hours a day or more were less likely to develop brain cancer than the participants who did less. The evidence was strongest for the over 50s.
Participants who walked for more than 72 minutes or jogged for longer than half an hour were not better protected than participants who did 36-72 minutes of walking or 15-30 minutes of jogging.
The most common form of brain cancer is glioma. In-vitro studies have shown that IGF-1 stimulates the growth of glioma cells. Williams believes that physical exercise helps the muscles to absorb more IGF-1 from the blood, making less IGF-1 available for cancer cell growth.
“Although our analyses cannot test whether exercise specifically improves survival in brain cancer patients, it is not unreasonable to expect that if physical activity decreases the risk of incident glioma, it might also extend survival “, Williams concludes.
Reduced risk of brain cancer mortality from walking and running.
This study aimed to test prospectively whether exercise is associated with lower brain cancer mortality in 111,266 runners and 42,136 walkers from the National Runners’ and Walkers’ Health Studies.
Hazard ratios and 95% confidence intervals (95% CI) from Cox proportional hazards analyses of mortality versus metabolic equivalent hours per day of exercise (MET-hours per day, where 1 MET = 3.5 mL O2·kg·min, or approximately 1-km run).
The National Death Index identified 110 brain cancer deaths during an 11.7-yr average follow-up. Runners and walkers were combined because the brain cancer risk reduction did not differ significantly between MET-hours per day run and MET-hours per day walked (P = 0.66). When adjusted for sex, age, race, education, and cohort effects, the risk for brain cancer mortality was 43.2% lower for those who exercised 1.8 to 3.5 MET·h·d (95% CI = 2.6%-66.8% lower, P = 0.04) and 39.8% lower for those who exercised ?3.6 MET·h·d (95% CI = 0.0%-64.0% lower, P = 0.05) compared with <1.8 MET·h·d at baseline. Pooling the runners and walkers who expended ?1.8 MET·h·d showed a 42.5% lower risk of brain cancer mortality for the entire sample (95% CI: 8.0 to 64.1, P = 0.02) and 40.0% lower risk when three deaths that occurred within 1 yr of the baseline survey were excluded (95% CI = 1.3%-62.4%, P = 0.04).
The risk for fatal brain cancer decreased in association with running and walking energy expenditure. Our ability to detect an exercise-brain cancer relationship may relate to the use of cohorts specifically designed to detect exercise-health associations, and the calculation of exercise energy expenditure from kilometers per day walked and run rather than time spent exercising.
PMID: 24091993 [PubMed – in process]