New York, December 4 -- Mobile phone usage has long been linked with raising the brain tumor risk. However, a novel research has debunked this notion, claiming that no significant changes in the cancer [abnormal cells that divide without control, which can invade nearby tissues or spread through the bloodstream and lymphatic system to other parts of the body.] rates have been reported from the time when mobile phone usage became widespread.

"If mobile phones were to cause brain tumors we would expect to see a sudden rise in the number of brain tumors at some point in time, and we don't see it," said lead researcher Isabelle Deltour from the Institute of Cancer Epidemiology at the Danish Cancer Society in Copenhagen.

Study details: To reach their conclusions, researchers examined data based on 60,000 brain tumor cases diagnosed over 30 years from 1974 to 2003.

Aged between 20 to 79 years, the study subjects hailed from the regions of Denmark, Finland, Norway and Sweden.

Researchers particularly focused on the incidence rates of two types of brain tumors: gliomas and meningioma.

During the study period, the incidence rate of cancers known as gliomas increased by 0.5 percent per year among men and 0.2 percent per year among women.

On the other hand, the incidence rate for cancers known as meningioma increased by 0.8 percent per year among men and 3.8 percent per year among women.

No increase in brain tumors seen

Researchers found that the incidence of brain tumors cases remained stable, decreased, or showed only a gradual increase over the 30 years study period.

"Either it means that mobile phones don't cause brain tumors or it means that we don't see it yet or we don't see it because the increase is too small to be observed in this population, or it is a risk that is limited to a small subgroup of the population," they marked.

Similarly, no substantial increase was found in the brain tumor cases between 1998 and 2003, a period when the cell phone usage had increased significantly.

"Our finding that brain tumor incidence rates were either stable, decreased, or continued a gradual increase that started before the introduction of mobile phones is consistent with mobile phone use having no observable effect on brain tumor incidence…,” the researchers concluded.

The radio frequency electromagnetic fields emitted from mobile phones are often associated with brain cancer risk. However, researchers could not identify the probable effects of mobile phone radiation [use of high-energy radiation from x-rays, neutrons, and other sources to kill cancer cells and shrink tumors] on the biological mechanism of cell phone users.

The study’s findings are published in Journal of the National Cancer Institute.

Further research needed: Though the study trends do not show any substantial alterations in the cancer rates, researchers opine that the issue is here to stay and it will not go away easily until clear cut answers are attained.

Therefore, the mobile phone users need to be studied for a longer time to determine whether long-term mobile usage causes brain tumors.

Another major reason which calls for further investigation is the high prevalence of mobile phone users.

Deltour said, "Because of the high prevalence of mobile phone exposure in this population and worldwide, longer follow-up of time trends in brain tumor incidence is warranted.”