Second-hand smoke linked to teen hearing loss

Teens who are exposed to second-hand smoke may be at increased risk of hearing loss, a new U.S. study suggests.

It's estimated that about 60 per cent of children in the U.S. are exposed to second-hand smoke. Exposure in the womb or during childhood is already tied to health conditions ranging from low birth weight to respiratory infections and behavioural problems.

Now researchers in New York say children who were exposed to cigarette smoke have higher rates of hearing loss.

The greater the exposure, the higher the risk, the study of 1,533 individuals aged 12 years to 19 showed.

Participants were interviewed about their health and family medical history, exposure to second-hand smoke and self-recognition of hearing impairment. They also had a physical exam that included a blood test that looked at exposure to nicotine, and hearing tests.

"The findings indicate that exposure to tobacco smoke is independently associated with an almost two-fold increase in the risk of hearing loss among adolescents," Dr. AnilLalwani and colleagues from NYU Langone Medical Center in New York City concluded inthe July issue of Archives of Otolaryngology Head and Neck Surgery.

Given that hearing loss early in life can cause problems with speech, language and cognitive development and functioning, the researchers said "these findings may have profound implications in light of the high exposure rates among adolescents in the United States."

Types of hearing loss tested

They suggested closely monitoring adolescents who are exposed to second-hand smoke for hearing loss.

In the study, participants had both their low- and high-frequency hearingtested. Low-frequency hearingprovides a sense of loudness and recognition of vowel sounds, said Lalwani. High-frequency hearing identifies consonants, helping to distinguish between words that sound similar, and it provides clarity to hearing.

Althoughthe study was large, it cannot show a cause-and-effect relationship, the authors said in pointing out limitations of the study. Also, information on prenatal exposure to second-hand smoke was not available for all participants.

It's not clear how second-hand smoke could affect the inner ear to the point of producing hearing loss, saidRobert Harrison, a senior scientist with Toronto's Hospital for Sick Children.

Harrison said he suspects it issomething to do with very early parental exposure during pregnancy or those early years in relation to ear infections. Exposure to recreational noise is another possibility, saidHarrison, who sits on the board of directors with the Hearing Foundation of Canada.

The investigators were unable to determine if earlier or long-term exposure is worse than later and short-term exposure.

The study was funded by the Zausmer Foundation and the U.S. National Institutes of Health.