A large study has found that teenagers exposed to secondhand cigarette smoke, gets into their ears, and is associated with hearing loss.
Exposed teens were 1.83 times more likely to experience low-frequency hearing loss compared to those with no exposure, according to Anil K. Lalwani, MD, and colleagues from New York University in New York City.
The adolescents experiencing the greatest risk for hearing loss -- a 2.72-fold increase - was in those with the highest levels of exposure as determined by serum cotinine levels, Lalwani's group reported in the July Archives of Otolaryngology-Head & Neck Surgery.
The list of potential damage caused by exposure to secondhand smoke continues to increase. They range from low birth weight to behavioral and cognitive problems and respiratory tract infections -- and more than half of U.S. children are exposed.
This is the first study to examine secondhand smoke exposure and hearing loss in adolescents. The researchers analyzed data from the 2005-2006 National Health and Nutrition Examination Survey (NHANES).
They identified 1,533 nonsmokers ages 12 to 19 who had undergone audiometric testing and whose serum cotinine levels had been measured. Cotinine is chemical byproduct of nicotine.
Less than one fifth (only 18.43%) of the teens with these forms of hearing loss were aware of the problem.
Other factors associated with hearing loss included a history of eczema, African American ethnicity, and having been cared for in a neonatal intensive care unit.
When participants were divided into quartiles by level of serum cotinine, the prevalence increased from 7.53% in nonexposed adolescents to 17.05% of those with the highest level of this marker of tobacco exposure (0.858 μg/L to 15 μg/L).
The researchers noted that the link of secondhand smoke exposure with elevated thresholds ranging from 0.5 kHz to 8 kHz suggests "that the injury to the inner ear is global."
In addition, the unilateral hearing loss is probably an early phase of ocular damage that is likely to progress in severity, they cautioned.
The elevated thresholds at 2, 3, and 4 kHz were particularly important, according to Lalwani and colleagues.
"These mid-to-high frequencies are critical for hearing in humans and are responsible for the clarity of hearing that allows us to discriminate between similar sounding words," they observed.
Possible mechanisms by which secondhand smoke could result in auditory damage include effects on the inner ear’s blood vessels and damage caused by nicotine or other cigarette ingredients.
Hearing loss in young children has been shown to interfere with not only speech and language development, but also cognitive function, academic progress, and social interaction.
But babies and young children are routinely screened for hearing difficulties, while adolescents are not.
The findings of this study suggest that teens who are exposed to secondhand smoke should have their hearing tested, and parents and caretakers should be made aware of the auditory hazards of their smoking.
The researchers acknowledged the study’s limitations included lack of information on regarding the length of and sources of secondhand smoke exposure -- including exposure prior to birth, and absence of information on other factors such as exposure to loud noises.
They concluded, "Future studies need to investigate the adverse consequences of this early hearing loss on social development, academic performance, behavioral and cognitive function, and public health costs."
Source: Archives of Otolaryngology-Head & Neck Surgery