Teens exposed to second -hand smoke may be at a higher risk of hearing loss, researchers have found.
The findings, which one expert called surprising, can't prove that second-hand smoke causes hearing loss. But the link is just one more reason to make sure that non smokers, especially kids, are protected from cigarette smoke, researchers said.
"We need to increase focus on this population at risk for hearing loss during adolescence that now have risk factors such as noise factors or second-hand smoke," said Dr Anil Lalwani.
Second-hand smoke has been tied to a range of health problems in kids, from respiratory infections to behavioural problems, although there is still no ironclad proof that smoke is at the root of all of these problems.
How tobacco affects kids’ inner ear
Dr Lalwani and his colleagues from New York University Langone Medical Centre thought tobacco smoke might have an effect on the blood flow in kids' inner ear.
They analysed data from a US national health survey, involving roughly 1,500 adolescents age 12 to 19. All of them had hearing tests in both ears and blood tests for levels of cotinine – which forms when the nicotine from cigarette smoke breaks down.
A very high level of cotinine suggests that a teen is a smoker, while a lower level means that kid is probably exposed to second-hand smoke.
Teens whose cotinine levels told researchers they spent a lot of time around smokers were more likely to have hearing loss at the lower frequencies of human speech than those without exposure to cigarette smoke.
Second-hand smoke even affects the voice
About 12% of the exposed kids had mild to severe hearing loss in one ear, compared to less than 8% of kids without smoke exposure.
The findings, which were scheduled to be published online in Archives of Otolaryngology – Head & Neck Surgery, also showed a trend toward significance for an effect on high-pitch sounds.
"It's kind of surprising," said Dr Joseph DiFranza, who has studied second-hand smoke at the University of Massachusetts Medical School in Worchester.
"We already knew that passive smoking is bad for children," Dr DiFranza, who wasn't involved in the new research, told Reuters Health. "This just piles on another reason" to make sure kids aren't exposed to second-hand smoke.
Adults that smoke are at risk too
While other studies haven't looked for a link between second-hand smoke and hearing loss in kids, Dr Lalwani said adults who smoke are known to be at higher risk of hearing loss themselves.
He said it will be interesting going forward to see if hearing loss in kids exposed to second-hand smoke could also explain some of the other problems seen in these kids, such as behavioural issues. For example, Dr Lalwani said that kids who can't hear a teacher's instructions are more likely to be labelled as having attention deficit hyperactivity disorder, or ADHD.
He added that doctors should be on the lookout for hearing problems in teens with second-hand smoke exposure. That's especially important because kids in this study with hearing loss usually didn't know they had a problem – but lack of hearing could be affecting their learning and speech skills, the researchers said.
Still, "the degree of hearing loss that they found in the study wasn't enough to say all kids should be tested for it because their parents smoke," said Dr DiFranza.
The researchers said that it's hard to tease out the effect of second-hand smoke exposure during childhood and adolescence from when kids were developing in the womb. But the new study suggests that "it's very toxic to the auditory system", Dr Lalwani told Reuters Health.
"We need to alter our public policies to protect the innocent bystanders who would otherwise be exposed to smoke," he added.
Preventing hearing loss
Causes of hearing loss
Symptoms of hearing loss
Image: Smoking in front of your children, Shutterstock