Body weight and physical activity levels may affect the risk of a certain brain cancers, new research suggests.
The study, published online Sept. 16 in the journal Neurology, found that excess weight was associated with a higher risk of a type of brain cancer known as meningioma. Obesity increased the risk of meningioma by 54 percent, and being overweight upped the risk by 21 percent, according to the study, which analyzed the findings of previously published research.
On the other hand, people who were physically active reduced their risk of meningioma by 27 percent, the researchers said.
“This is an important finding since there are few known risk factors for meningioma and the ones we do know about are not things a person can change,” said meta-analysis author Gundula Behrens, PhD, of the University of Regensburg in Regensburg, Germany. “Given the high prevalence of obesity and the unfavorable prognosis for this type of tumor, these findings may be relevant for strategies aimed at reducing the risk of meningioma.”
The study also found that being heavier was not linked to the risk of a second, deadlier form of brain cancer called glioma. And while there was a weak association between more physical activity and a lower risk of glioma, the researchers said the finding wasn’t statistically significant.
While the research was able to show an association between weight and physical activity and the risk of meningioma, it wasn’t designed to prove a cause-and-effect relationship.
Incidence of brain tumors increases with higher BMI
Meningioma and glioma are the most common types of brain tumors in adults, according to background information in the study. However, these tumors are still rare. Annually, about five to eight people of every 100,000 will be diagnosed with meningioma. About five to seven of every 100,000 people will receive a glioma diagnosis in a given year, the study authors said.
At five years following a diagnosis, 63 percent of people with meningioma will still be alive. Glioma is far more deadly, with only a 4 percent survival rate at five years, the study reported.
The current research was a review of 18 previous studies involving more than 6,000 people. About half the patients had meningiomas, and the other half had gliomas. Some of the studies compared patients with healthy counterparts. Twelve of the studies looked at body mass index and cancer risk, and six looked at physical activity and cancer risk.
The studies defined obesity as a body mass index (BMI) over 30 and overweight as a BMI from 25 to 29.9. Body mass index is a measurement that provides a rough estimate of body fat based on height and weight. Physical exercise was rated as high or low in the studies.
In addition to effects of weight and exercise on meningioma risk, the study authors found a 32 percent reduced glioma risk among underweight teens (BMI less than 18.5).
These results support previous findings from a 2008 study published in the British Journal of Cancer, which concluded that “the incidence of glioma or meningioma tumors increases with … increasing BMI.”
Physical inactivity and overweight as cancer risk factors
How excess weight or physical activity might affect the development of certain brain tumors is unclear. One possible explanation, the study authors said, is that people with excess weight produce excess estrogen, and estrogens promote meningioma development. Insulin levels could be a factor for the same reason, the authors speculated.
The relationship between meningioma risk and exercise may be more complicated. Behrens and her co-authors noted that brain tumor symptoms could have led some patients to reduce their normal physical activity even before their diagnosis. These patients might have reported low activity levels because their brain cancer slowed them down before they knew they had it, the researchers said.
Can someone who is already overweight or obese do anything to take advantage of this information? The researchers think so. “It’s plausible that exercise and weight reduction may help prevent the meningioma formation in persons already at risk for these tumors,” they concluded.
Physical activity and weight loss may also cut the risk of other types of cancer. According to a 2014 study published in The Lancet, being overweight increases the risk of developing at least 22 different cancers, including cancers of the breast, ovaries, uterus, kidneys, colon, rectum, liver, and thyroid. Another 2014 study, published in The Lancet Oncology, estimated that nearly half a million new cancer cases each year can be attributed to high body mass index, with 110,000 of those cases — almost a quarter of the global BMI-related cancer burden — occurring in North America.
But physical inactivity can be just as deadly as obesity, according to a study published earlier this year in the American Journal of Clinical Nutrition (AJCN). The study looked at the link between physical inactivity and premature death, and its interaction with obesity, in a group of more than 300,000 people, and found that sedentary behavior was associated with twice the number of premature deaths as obesity.
From a public health perspective, it is as important to increase levels of physical activity as it is to reduce the levels of obesity — maybe even more so, said Dr. Ulf Ekelund, a sport medicine professor for the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge in the UK, and the first author of the AJCN article.
“We estimated that eradicating physical inactivity in the population would reduce the number of deaths twice as much as if obesity was eradicated,” Ekelund said.