There's no question about it: Smoking cigarettes does affect a person's ability to hear. Not only that, but the number of cigarettes smoked may also have an impact on your risk (although there is disagreement on whether that is true). The length of time you smoke, though, definitely increases the risk.
It has long been known that smoke has dangerous effects on the ear. As far back as 1962, scientists did a study with guinea pigs. The guinea pigs were deliberately forced to inhale smoke, and then killed. When the scientists examined the dead guinea pigs' cochleas (the cochlea is in the inner ear and plays a key role in how we hear), they found evidence of degeneration. If that is what happens with animals, what happens with humans? For obvious reasons, this type of study could not be duplicated with humans because it involved the forced inhalation of smoke.
Several studies have been done internationally that demonstrate the link between smoking and hearing loss. Smoking is now considered a known risk factor for hearing loss. The studies varied in size, but in each of them, smokers and former smokers had more hearing loss than people had never smoked.
European Study of Smoke and Hearing Loss
In Europe, a study was done with 4,083 participants at audiology centers. The participants were all between 53 and 67 years old. Each participant filled out a medical history questionnaire, self-reporting their smoking status. On the questionnaire, participants were asked if they had smoked regularly, for how many years they had smoked, and how many cigarettes they had daily. A common term in smoking studies is "packyear." For this study, the authors defined packyear by multiplying the time in years that a person had smoked, by a weighting factor for how many cigarettes a day they had smoked. E.g., less than ten cigarettes a day received a weight factor of 0.5, while more than 20 cigarettes daily had a weight factor of 1.5.
The results showed a "significant" association between the number of packyears and high frequency hearing loss. In their analysis, the authors pointed out that smoking affects the middle ear by irritating the Eustachian tube and the lining of the middle ear (the middle ear also plays a key role in our hearing mechanism because it is home to the auditory ossicles).
Asian Study of Smoke and Hearing Loss
Researchers in Asia did a small study of 263 people in a rural area with the goal of examining the combined impact of aging and smoking on hearing loss. None of these people had been exposed to much noise (noise exposure is a known factor in hearing loss). They found that the prevalence rate of hearing loss for smokers aged 40 and under was 11.9%; but for smokers older than 40, it was much higher -- 51.3 percent. Among nonsmokers 40 and younger, the prevalence rate was just 6.9%; for nonsmokers older than 40 it was only 29.7 percent. In other words, as the smokers became older, their risk for hearing loss increased exponentially.
Israeli Study of Smoke and Hearing Loss
Researchers in Israel did a larger study of 13,308 men between 20 and 68 years old, with the average being 34.6 years old. As with the other studies, this one included current smokers, former smokers, and nonsmokers. What was interesting about the results of this study is that it showed a higher risk of hearing loss in younger adults! Participants over 35 years old had only a 17% risk increment, but participants under 35 had a 43% risk increment. Not only that, the researchers found a "significantly" higher incidence of any type of hearing loss in both the current smokers (11.8%) and past smokers (11.7%) than in people who had never smoked. The ones who had never smoked had only an 8.1% incidence of hearing loss.
The other data revealed by the study was a "non-significant" relationship between the number of cigarettes smoked and hearing loss.
They also found that conductive hearing loss was more common than sensorineural hearing loss -- 6.1% of the smokers and the same percentage of the former smokers had conductive hearing loss, as did 3.3% of the nonsmokers. Current smokers had a 1.5% incidence of sensorineural hearing loss; former smokers had a 1.2% incidence, and once again, the nonsmokers had the lowest incidence -- just 0.7%.
Overall, the researchers found that smoking increases the risk of developing a hearing loss by 45 percent.
American Study of Smoking and Hearing Loss
Researchers in the United States have done their own studies of the relationship between smoking and hearing loss. In one American study, 3,753 participants between 43 and 84 years old (average age was 65.8 years) living in a Wisconsin town self-reported their smoking history as part of a hearing study. The results showed that current smokers were 1.69 times more likely to have hearing loss than people who had never smoked.
For this study, packyears were determined by dividing the number of cigarettes smoked daily by 20 cigarettes per pack, and then multiplying that result by the number of years a person had smoked. The average number of packyears for current smokers was 34.9, and it was 28.2 packyears for former smokers. Just as with the Israeli study, the American researchers found the amount of exposure appeared to have little impact. Those with the most packyears were only 1.30 times as likely to have a hearing loss as those with no packyears.
However, in every age group that participated in the Wisconsin study, the prevalence of hearing loss was greater in current smokers than in nonsmokers. When the researchers considered the effect of occupational noise exposure, they found that there was a significant association between smoking and hearing loss for both people who had been exposed to occupational noise, and those who had not been exposed to occupational noise. In their analysis, the researchers theorized that smoking may do "direct" toxic harm to the hair cells that help us to hear.
Concluding Thoughts on Smoking and Hearing Loss
Smoking may significantly increase your risk of hearing loss. If you are a smoker, you are encouraged to check out the About.com Quit Smoking site, which provides plenty of resources for helping you quit and stay smoke-free. If you have loved ones who smoke, you may wish to show them this article as another reason to try to stop smoking.
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