Passive smoking may make teens deaf -- study

According to the findings of a new study, teens' exposure to secondhand smoke more than doubles their risk of hearing loss than those who are not exposed to tobacco smoke.

While exposure to secondhand smoke is already known to cause a range of health ailments, including low birth weight, respiratory infections and behavioral problems, the study, first of its kind to examine secondhand smoke exposure and sensorineural hearing loss in adolescents, found that children exposed to secondhand smoke are more likely to develop recurrent otitis media.

"Second hand smoke may also have the potential to have an impact on auditory development, leading to sensorineural hearing loss (SNHL)," Anil K. Lalwani, from NYU Langone Medical Center in New York City marked.

The study
For the purpose of the study, the researchers analyzed cross-sectional data from the 2005-2006 U.S. national health survey.

The researchers identified over 1,500 teenage non-smokers, all of whom had undergone audiometric testing.

The teenagers underwent preliminary evaluation at their homes. They were interviewed about their health status, family history, exposure to secondhand smoke and self-recognition of hearing trouble.

"Second hand smoke may also have the potential to have an impact on auditory development, leading to sensorineural hearing loss (SNHL)," Anil K. Lalwani, from NYU Langone Medical Center in New York City marked.

The participants then underwent audiometric testing and blood screening for levels of cotinine - a nicotine chemical.

While very high levels of cotinine in blood suggest that the person is a smoker, a lower level indicates exposure to secondhand smoke.

Furthermore, in non-smokers, teenagers with higher cotinine levels, suggests prolonged exposure to secondhand tobacco smoke.

Study findings
Investigators found that teenagers with relatively high blood cotinine levels were more likely to suffer hearing problems at the lower frequencies than those without exposure to secondhand tobacco smoke.

The kids with the highest levels of serum cotinine were at the greatest risk for hearing loss, a 2.72-fold increase, researchers found.

Exposed teenagers were 1.83 times more likely to suffer from low-frequency hearing loss than those who were not exposed.

Low-frequency sensorineural hearing loss is defined as a pure-tone level above 15 dB for 0.5, 1, and 2 kHz, while high-frequency loss is a level above 15 dB for 3, 4, 6, and 8 kHz.

Statistically, nearly 12 percent of the passive smokers suffered from mild to severe hearing loss in one ear vis-à-vis less than 8 percent teens who were not exposed to secondhand smoke.

No self-recognition of hearing trouble
Surprisingly, 80 percent of participants who were diagnosed with hearing loss were unaware they had any hearing problem.

As milder hearing loss is not always noticeable, children exposed to secondhand smoke should be “regularly screened,” Lalwani said.

The findings of the study are published in the current issue of the journal 'Archives of Otolaryngology -- Head & Neck Surgery.'