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Surprising study results. The question is why would having higher education somehow be associated with higher incidence of brain tumors? Is there something about sitting and studying, or sitting in an office for hours on end - perhaps next to something with high electromagnetic fields, that leads to this result? Or is it what a study in mice found last year - that the activity of 'thinking" or nerve activity in the cerebral cortex actually fuels the growth of brain tumors? From Medical Xpress:

High levels of education linked to heightened brain tumor risk

A university degree is linked to a heightened risk of developing a brain tumour, suggests a large observational study, published online in the Journal of Epidemiology & Community Health. Gliomas, in particular, were more common among people who had studied at university for at least three years than they were among those who didn't go on to higher education, the data show.

The researchers base their findings on more than 4.3 million Swedes, all of whom were born between 1911 and 1961 and living in Sweden in 1991. They were monitored between 1993 and 2010 to see if they developed a primary brain tumour, and information on educational attainment, disposable income, marital status, and occupation was obtained from national insurance, labour market,and national census data. During the monitoring period, 1.1 million people died and more than 48,000 emigrated, but 5735 of the men and 7101 of the women developed a brain tumour.

Men with university level education, lasting at least three years, were 19% more likely to develop a glioma—a type of cancerous tumour arising in glial cells that surround and support neurons in the brain—than men whose educational attainment didn't extend beyond the period of compulsory schooling (9 years). Among women, the magnitude of risk was 23% higher for glioma, and 16% higher for meningioma—a type of mostly non-cancerous brain tumour arising in the layers of tissue (meninges) that surround and protect the brain and spinal cord—than it was for women who didn't go on to higher education.

High levels of disposable income were associated with a 14% heightened risk of glioma among men, but had no bearing on the risk of either meningioma or acoustic neuroma—a type of non-cancerous brain tumour that grows on the nerve used for hearing and balance. Nor was disposable income associated with heightened risk of any type of brain tumour among the women.

Occupation also seemed to influence risk for men and women. Compared with men in manual roles, professional and managerial roles (intermediate and high non-manual jobs) were associated with a 20% heightened risk of glioma and a 50% heightened risk of acoustic neuroma. The risk of glioma was also 26% higher among women in professional and managerial roles than it was for women in manual roles, while the risk of meningioma was 14% higher.

This is an observational study so no firm conclusions can be drawn about cause and effect, and the researchers point out that they were not able to glean information on potentially influential lifestyle factors. But they emphasise that their findings were consistent, and they point to the strengths of using population data.  (Original study)

The latest results on this hotly debated subject. The researchers suggest that people instead use "hands free phones with the loud speaker feature". From Medscape:

Long-Term Cell Phone Use Linked to Brain Tumor Risk

Long-term use of both mobile and cordless phones is associated with an increased risk for glioma, the most common type of brain tumor, the latest research on the subject concludes.

The new study shows that the risk for glioma was tripled among those using a wireless phone for more than 25 years and that the risk was also greater for those who had started using mobile or cordless phones before age 20 years.

The recent worldwide increase in use of wireless communications has resulted in greater exposure to radio frequency electromagnetic fields (RF-EMF). The brain is the main target of RF-EMF when these phones are used, with the highest exposure being on the same side of the brain where the phone is placed.

The analysis included 1498 cases of malignant brain tumors; the mean age was 52 years. Most patients (92%) had a diagnosis of glioma, and just over half of the gliomas (50.3%) were the most malignant variety — astrocytoma  grade IV (glioblastoma multiforme). Also included were 3530 controls, with a mean age of 54 years.

The analysis showed an increased risk for glioma associated with use for more than 1 year of both mobile and cordless phones after adjustment for age at diagnosis, sex, socioeconomic index, and year of diagnosis. The highest risk was for those with the longest latency for mobile phone use over 25 years.

The risk was increased the more that wireless phones were used. The odds ratios steadily rose with increasing hours of use...Further, the risk was highest among participants who first used a mobile phone (odds ratio, 1.8) or cordless phone (odds ratio, 2.3) before age 20 years, although the number of cases and controls was relatively small.

As Dr Hardell explained, children and adolescents are more exposed to RF-EMF than adults because of their thinner skull bone and smaller head and the higher conductivity in their brain tissue. The brain is still developing up to about the age of 20 and until that time it is relatively vulnerable, he said.

There was a higher risk for third-generation (3G) mobile phone use compared with other types, but this was based on short latency and rather low numbers of exposed participants, said the authors. 3G universal global telecommunications system mobile phones emit wide band microwave signals, which "hypothetically" may result in higher biological effects compared to other signals, they write. 

Numerous studies have looked at the link between use of wireless phones and brain tumors. Studies by Dr Hardell and his colleagues dating back to the late 1990s have found a connection with mobile and cordless phones. But the INTERPHONE study (Int J Epidemiol 2011;39:675-694; Cancer Epidemiol 2011;32:453-464) failed to find strong evidence that mobile phones increase the risk for brain tumors.

In addition, a large prospective study (Int J Epidemiol 2013;42:792-802) found that mobile phone use was not associated with increased incidence of glioma or of meningioma or non–central nervous system cancers in middle-aged British women.

Pathophysiology. Published online October 28, 2014. Abstract