Adolescent Hearing Loss Has Roots in Secondhand Smoke

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A new study among adolescents found that exposure to secondhand smoke (SHS) may lead to the most common type of hearing loss, sensorineural hearing loss (SNHL). This type of hearing impairment typically cannot be corrected surgically or medically.

Most children are exposed to secondhand smoke

Secondhand smoke is the combination of smoke released by burning tobacco products along with the smoke exhaled by smokers. More than 7,000 chemicals are in secondhand tobacco smoke, and at least 250 of them are known to be harmful. About 60 percent of US children are exposed to this smoke, which has been implicated in previously identified--and now a new--health-associated issue.

In a new study, Anil K. Lalwani, MD, and a team from New York University Langone Medical Center, evaluated the risk factors for sensorineural hearing loss among 1,533 nonsmoking teens ages 12 to 19 years who had participated in the National Health and Nutrition Examination Survey from 2005 to 2006. Results of the study appear in the July issue of Archives of Otolaryngology—Head and Neck Surgery.

Based on the adolescents’ responses to questions about their health, medical history, exposure to secondhand smoke, and any self-recognition of hearing problems, as well as results of blood testing for cotinine (a nicotine breakdown by-product) and hearing tests, the researchers determined that adolescents exposed to secondhand smoke had more low- and high-frequency hearing loss than those with no exposure.

In addition, most (80%) of the teens did not realize they had lost some of their hearing. The blood tests also revealed that as the level of cotinine rose, so did the rate of hearing loss.

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Hearing loss is usually categorized based on which part of the auditory system is affected. The type of hearing loss evaluated in the current study, SNHL (sensorineural hearing loss) occurs when the inner ear (cochlea) or the nerve channels from the inner ear to the brain are damaged. SNHL is the most common type of permanent hearing loss, and it usually cannot be surgically or medically corrected.

Sensorineural hearing loss can be caused by head trauma, a malformation of the inner ear, illness, medications that are toxic to the auditory system, genetics or heredity, exposure to loud noise, and aging. With SNHL, individuals have a reduced ability to hear faint sounds, and even when voices are loud enough to hear, they may be muffled or unclear.

A number of studies have named secondhand smoke as causing health problems in children. A new study in Pediatrics notes that smoke exposure increased the risk of neurobehavioral disorders in children, including learning disabilities, ADHD, and conduct disorders.

In a large retrospective analysis of data from 192 countries, researchers reported in Lancet in January 2011 that worldwide, 40 percent of children were exposed to secondhand smoke in 2004, and that of the 603,000 deaths attributed to secondhand smoke, 28 percent were in children. The largest disease burdens were associated with lower respiratory infections in children younger than 5 years (nearly 6 million cases) and asthma in children (651,000).

The authors of the new study in the Archives point out that “adolescents who are exposed to SHS may need to be more closely monitored for hearing loss,” and that they “should be educated about risk factors for hearing loss, such as recreational or occupational noise exposure.”

SOURCES:
Kabir Z et al. Pediatrics 2011 Jul 11
Lalwani AK et al. Archives of Otolaryngology—Head and Neck Surgery 2011; 137(7): 655-62
National Cancer Institute
Oberg M et al. Lancet 2011 Jan 8; 377(9760): 139-46

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