Tuesday, August 2, 2011

Secondhand Smoke Associated With Hearing Loss in Teens

From Medscape Education Clinical Briefs

News Author: Emma Hitt, PhD
CME Author: Laurie Barclay, MD

Clinical Context

Approximately 60% of US children are exposed to secondhand smoke (SHS). Prenatal or childhood SHS exposure has been linked to low birth weight, respiratory tract infections, behavioral problems, otitis media, and various other health conditions.
It has also been suggested, but not previously studied, that SHS may negatively affect auditory development, potentially causing sensorineural hearing loss (SNHL). Possible mechanisms could include impaired in utero development; low birth weight; and/or cochlear, vestibulocochlear nerve, or brain damage. The objective of this study by Lalwani and colleagues was to examine risk factors for SNHL in different subgroups of adolescents based on age, sex, race/ethnicity, and income or poverty level.

Study Synopsis and Perspective

SHS may result in a nearly 2-fold increase in SNHL in adolescents, suggesting that monitoring for early hearing loss with periodic audiologic testing may be required in this population.
Anil K. Lalwani, MD, and colleagues with the New York University Langone Medical Center, in New York, NY, reported the findings in the July issue of the Archives of Otolaryngology—Head and Neck Surgery.
According to the researchers, recurrent acute otitis media is more common in the nearly 60% of children exposed to SHS in the United States. They suggest that increased risk for otitis media with SHS may be caused by several factors including "suppression or modulation of the immune system, enhancement of bacterial adherence factors, the consequence of exposure to toxins within SHS, and impairment of the respiratory mucociliary apparatus, leading to Eustachian tube dysfunction."
In the current study, Dr. Lalwani and colleagues evaluated cross-sectional data from the National Health and Nutrition Examination Survey (2005-2006), which included information on 1533 participants 12 to 19 years old who underwent audiometric testing and serum cotinine measurements and who were nonsmokers.
The investigators defined SNHL as an average pure-tone level greater than 15 dB for 0.5, 1, and 2 kHz (low frequency) and 3, 4, 6, and 8 kHz (high frequency).
Exposure to SHS, as determined by serum cotinine levels, was associated with elevated pure-tone hearing thresholds at 2, 3, and 4 kHz and a higher rate of unilateral low-frequency SNHL (11.82% vs 7.53%; P = .04). In addition, multivariate logistic regression analyses indicated a 1.83-fold increased risk for unilateral low-frequency SNHL (95% confidence interval, 1.08 - 3.41).
According to the researchers, there was a direct relationship between the prevalence of SNHL and SHS exposure. Moreover, nearly 82% of adolescents with SNHL did not know that they had hearing difficulties.
"This study demonstrates, to our knowledge for the first time, a relationship between tobacco smoke exposure and hearing loss among adolescents in the United States," they conclude. "These findings may have profound implications in light of the high exposure rates among adolescents in the United States."

Arch Otolaryngol Head Neck Surg. 2011;137:655-662.

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