When Smoke Comes Out the Ears

Smoking during pregnancy linked to hearing loss in teens

(RxWiki News) Most people associate health problems from smoking with the lungs. But smoking is linked to other health issues as well, like hearing loss — even for babies exposed in the womb.

A recent study found that hearing loss was more common in teens whose moms smoked during pregnancy than among teens whose moms did not smoke.

More than twice as many of the teens who were exposed to tobacco smoke in the womb had hearing loss when compared to those without smoke exposure during pregnancy.

"Don't smoke while pregnant."

The study, led by Michael Weitzman, MD, of the Department of Pediatrics at New York University School of Medicine, looked at whether exposure to tobacco smoke in the womb was related to hearing loss.

Past research has already linked smoking and secondhand smoke to sensorineural hearing loss.

Sensorineural hearing loss occurs when the inner ear or part of the brain is damaged. The inner ear is the nerve running from the ear to the brain.

The researchers gave hearing tests to 964 teens, aged 12 to 15, who were part of the National Health and Nutrition Examination Survey 2005-2006.

The researchers also interviewed the participants about smoking or secondhand smoke exposure and tested their blood for cotinine, a chemical found when a person smokes or is exposed to secondhand smoke.

Overall, 16.2 percent of the teens' mothers had smoked during pregnancy.

The researchers found that more of the participants exposed to smoke during pregnancy had sensorineural hearing loss than those not exposed to smoke.

Sensorineural hearing loss was identified in 17.6 percent of the teens whose mothers smoked during pregnancy, compared to 7.1 percent of teens whose mothers did not smoke during pregnancy.

This finding was after the researchers took into account whether the teens smoked or were currently exposed to secondhand smoke.

The researchers had also taken into account the teens' race/ethnicity, their family income, their birth weight, how much noise they were exposed to, whether they had spent time in the neonatal intensive care unit (NICU) after birth and whether they had three or more episodes of ear infections, allergies or eczema.

Teens whose mothers smoked during pregnancy were therefore 2.6 times more likely to have hearing loss than if their mothers did not smoke during pregnancy, even after taking into account other factors that might influence hearing loss.

"The actual extent of hearing loss associated with prenatal smoke exposure in this study seems relatively modest," the researchers wrote.

"The largest difference in pure-tone hearing threshold between exposed and unexposed adolescents is less than 3 dB, and most of the hearing loss is mild," they wrote.

"However, an almost 3-fold increased odds of unilateral hearing loss in adolescents with prenatal smoke exposure is worrisome for many reasons," they wrote.

They noted that even mild hearing loss can interfere with a child's ability to learn and communicate. They also said that hearing loss may become more likely and/or worse as the participants age.

Andre F. Hall, MD, board certified obstetrician/gynecologist at Birth and Women's Care in Fayetteville, NC, said "...smoking during pregnancy is frowned upon both for risks that are known to the fetus and those that are as of yet unknown. To date, I am unaware of other studies which have specifically linked smoking to hearing loss in an unborn child. That said, however, logic would dictate that one consider this a real possibility given what we know about smoking and nerve damage in general.

He continued, "I also believe that this study's relative small size (964 participants) and no other studies of its kind warrant caution prior to making cause and effect conclusions. Additional studies looking at these specific issues are needed. In the meantime, because of the abundance of information we do know about smoking in pregnancy, it would be wise for these women to avoid smoking themselves or exposure via secondhand smoke."

The study was published June 20 in the journal JAMA Otolaryngology—Head & Neck Surgery. Information regarding funding was not provided. The authors declared no conflicts of interest.

Review Date: 
June 18, 2013