Do cell phones cause brain tumors? The question has been asked since the phones first arrived on the scene, and now one of the largest studies ever to examine the issue shows that the answer is no.

The new report is in line with most other large studies and should reassure the hundreds of millions of regular cell phone users around the world.

But questions remain about the safety of long-term cell phone use, since the studies reported to date have followed subjects for no more than a decade.

Other Brain Diseases

And it is not yet clear if the phones raise the risk of other brain and central nervous system diseases, says Christoffer Johansen, MD, PhD, who has long studied cell phone use along with colleagues from the Danish Cancer Society.

What we can say is that we now know that people who have used mobile phones for 10 years or less do not seem to be at increased risk for the most commonly seen brain tumors, he tells WebMD.

But we don't know very much about usage for more than 10 years, or whether or not mobile phones are associated with other brain diseases like Alzheimer's and multiple sclerosis.

In the new study, researchers compared the cell phone usage histories of 966 patients with glioma-type brain tumors with 1,716 people without tumors matched for age, sex, and place of residence.

The four-year investigation included people living in urban and rural locations within England and Scotland. It is reported in the Jan. 21 issue of BMJ.