Passive smoking and link to hearing loss
exposure has been linked to hearing loss
, according to a new US report.
Dr Anil Lalwani, a paediatrics professor at New York University and co-author of the study explains: "We know that second-hand smoke is associated with ear infections. We wanted to see if there were detrimental consequences of second-hand smoke for kids who do not actually smoke but are still exposed to smoke."
Dr Lalwani and his team looked at the risks to American teens of sensorineural hearing loss - an irreversible condition. 1,533 youngsters took part in the National Health and Nutrition Examination Survey from 2005 to 2006.
The teenagers were interviewed about their health and family medical histories, exposure to second-hand smoke and their own recognition of hearing impairment. They also took a physical exam which included testing for cotinine which is a by-product of nicotine exposure - and hearing tests.
"What we found was in both low and high-frequency hearing. Hearing was worse in individuals exposed to smoking, statistically so for low-frequency," said Dr Lalwani.
Although Dr Lalwani believes further studies will build on his team's report, others are sceptical. Robert Harrison, a senior scientist with Toronto's Hospital for Sick Children, said he was surprised by the findings, since he could not see how second-hand smoke could affect the inner ear to the point of producing hearing loss.
"There is some relationship, but I suspect it's a non-causal relationship because of the possibility of recreational noise exposure," he says. "Or it is something to do with very early parental exposure during pregnancy or those early years in relation to middle ear infection."
Roberta Ferrence, a senior scientist with the Centre for Addiction and Mental Health in Toronto, said health problems associated with the duration of second-hand smoke exposure seem to be the biggest factor.
"People think active smoking is far more serious, and generally it is," she said. "But it depends on what age you're exposed. Most kids don't start smoking until they're in their teens. However, they may actually have been exposed in the womb, so they'd be starting off with many years of exposure to second-hand smoke. At times when the body is developing, an infant is certainly more vulnerable than a 14-year-old."
She added that since young children also breathe more rapidly, there may be internal exposure as a result of the smoke.
Dr Lalwani believes that the "incredible negative consequences" of second-hand smoke is now commonly accepted, concluding that "This has huge implications for public health."
Commented Emma Costin, Head of Industrial Disease
for Simpson Millar LLP: "The findings from New York are surprising to the lay person and clearly on the medical side there is a lack of understanding of the physiological mechanism by which second hand smoke can affect the hearing of children and young people. Nevertheless this is fascinating research and underlines yet another link between environment and disease. It is important that new and would be parents continue to be educated about the need to avoid subjecting children to passive smoking."