Sept. 19, 2007 -- Long-time mobile phone users who talk more than an hour a day on the devices may be may be more likely to have high-frequency hearing loss, researchers say.
"Our intention is not to scare the public," says Naresh K. Panda, MS, DNB, chairman of the department of ear, nose, and throat at the Post Graduate Institute of Medical Education and Research in Chandigarh, India, and researcher for the study. The study, he tells WebMD, is preliminary and small. "We need to study a larger number of patients."
He presented the findings Wednesday at the annual meeting of the American Academy of Otolaryngology -- Head and Neck Surgery in Washington.
His team found that people who had talked on cell phones for more than four years and those who talked more than an hour daily were more likely to have these high-frequency losses. These losses can make it difficult to hear consonants such as s, f, t and z, making it hard to understand words.
But another hearing expert familiar with the study says there is as yet no cause for alarm.
Hearing Loss Study
Panda and his colleagues evaluated 100 people, aged 18 to 45, who had used mobile phones for at least a year, dividing them into three groups according to length of use. One group of 35 had used phones for one to two years; another group of 35 had used them for two to four years, and a group of 30 had used them for more than four years.
"We asked them if they had been using the phones less than 60 minutes or more than 60 minutes per day," Panda tells WebMD. They compared the phone users with 50 people who had never used cell phones and served as a control group. The study was conducted in India.
Those who used the mobile phones for more than four years had more hearing loss in high-frequency ranges in their right ear, the ear most held the phone to, than those who used the mobile phone for one to two years.
"When we compared high-frequency thresholds (the level at which the sound is first detected) between the one- to two-year [users] and more than four years; there was a significant difference in the thresholds between these two groups," he says.
One- to two-year users had a 16.48 decibel loss in the high-frequency range, he says, while those who used the phones more than four years had a 24.54 decibel loss.
That decrease in hearing over a relatively brief period may not be noticeable to mobile phone users but would be of concern to a hearing expert, says Andy Vermiglio, AuD, a research audiologist at House Ear Institute in Los Angeles.
Mobile phone users who had symptoms such as a warm sensation, fullness in the ears, or ringing were more likely to have the high-frequency hearing loss, Panda also says.
Long-term mobile phone use may result in inner ear damage, Panda speculates. And symptoms such as ear warmth or fullness could be early warning signs of that damage.
The research is too preliminary to warrant alarm, says Chester Griffiths, MD, chairman of the surgery department at Santa Monica -- UCLA Medical Center and Orthopaedic Hospital and assistant clinical professor at the David Geffen School of Medicine at the University of California Los Angeles. He was not involved in the study but reviewed the findings for WebMD.
"Based on this study, I would not advise any change at the point, but I would caution people if they have any symptoms to stop using a cell phone or to reduce use."
Cell Phone Industry Responds
Joe Farren, a spokesman for CTIA -- the Wireless Association, the industry organization for the cellular industry, tells WebMD he has not reviewed the new study closely so he can't comment directly on the findings.
But he tells WebMD that previous research has not found a link between cell phone use and harmful health effects.
"There have been numerous studies conducted around the globe that have been peer-reviewed and published in leading scientific journals that show no association between wireless usage and adverse health effects," Farren says.
The subjects in the Indian study used GSM mobile phones. Farren says U.S. mobile phone users have phones that use the GSM platform but also other platforms.
Panda plans to continue his research. Meanwhile, his advice to preserve hearing: "Use cell phones when absolutely necessary.