Passive smoking, or regularly breathing in smoke from other people’s cigarettes, is linked to some degree of hearing loss in non-smokers, say US researchers in a leading journal.
The study, conducted by researchers from the University of Miami, the International University of Florida, also in Miami, and Starkey Laboratories, a hearing technology company in Eden Prairie, Minnesota, was published this week in BMJ’s Tobacco Control.
Doctors have known for some time that regular smokers are at higher risk of hearing loss, but until this study it was not clear if this might also be the case for passive smoking.
For the study, the researchers used 1999-2004 data from the National Health and Nutrition Examination Survey (NHANES), a yearly survey which covers a nationally representative cross-section of US households and where the participants also undergo a physical examination and give blood samples.
The data they analyzed belonged to 3,307 current non-smokers aged 20 to 69 years whose blood samples classed them as passive smokers because of the level of cotinine, a tobacco smoke constituent, in their blood.
All the participants had also undergone hearing tests and given complete data on medical history, level of noise exposure and smoking history (for instance had they ever smoked and/or lived with a smoker).
The degree of hearing loss in each ear was measured by testing the ability to hear pure tones over a range of frequencies from low and mid (500, 1000 and 2000 Hz) to high (3000, 4000, 6000 and 8000 Hz).
The results showed that among this group of passive smokers:
- Men were significantly more likely to have high frequency hearing loss, as were older participants and those with diabetes; and this was regardless of whether they had smoked in the past or not.
- Even after controlling for these (gender, age, diabetes) and other potential confounders, passive smoking was linked to impaired hearing.
- Former smokers were significantly more likely to have some degree of hearing loss, with nearly half of them having high frequency hearing loss.
- Among never smokers, the risk was not as strong: although nearly one in 10 had low to mid frequency hearing loss and just over one in four had high frequency hearing loss.
The researchers noted that the stronger findings among former smokers suggests that if you continue to breathe in other people’s tobacco smoke, even at low levels, the gradual loss of hearing that starts when you take up smoking does not necessarily stop when you give up.