According to a 1998 study with over 3,000 participants, smokers are 70% more susceptible to hearing loss than non-smokers. But another more recent 2004 study found no real link between smoking and hearing loss. So, who’s to be believed?
Over the past 40 years, the medical community has recognized the danger smoking presents to hearing health. But because the hearing process is extremely complex, pinpointing how smoking affects hearing is not so simple. This does not mean that smoking does not affect hearing loss — only that how it affects hearing loss is not entirely clear.
More recent studies, like this five-year study by The Blue Mountains Hearing Group published in 2010, have also found smoking to have deleterious effects in individuals not exposed to occupational noise hazards. A 2011 study in mice discovered that inhaling cigarette smoke alone may not be damaging to hearing, but exposure to both smoke and noise did lead to hearing impairment.
Lastly, a very recent 2013 study found that passive smoking and the inhalation of secondhand smoke caused minimal sensorineural hearing loss in children aged 5–11 years. Sensorineural hearing loss refers to hearing loss caused by damage to either the hairs lining the cochlea or to the auditory nerve. Unlike outer or middle-ear related hearing loss, sensorineural hearing loss is the most damaging and cannot yet be treated.
How smoking may be damaging hearing
First of all, we should all keep in mind that smoking has been proven to be deleterious to our health, and is strongly tied to lung cancer, heart disease, and a variety of other tobacco-related health risks. Additionally, smoking has been implicated in two distinct forms of hearing loss.
The myriad of dangerous chemicals in cigarette smoke, including formaldehyde, benzene, arsenic, vinyl chloride, ammonia, and hydrogen cyanide, may affect both conductive hearing (middle ear vibrations) as well as inner ear hearing by damaging the hair cells lining the cochlea. In many studies, there is also a strong correlation between the number of cigarettes smoked and the degree of hearing loss. In other words, smoking-related hearing loss is dose-dependent.
While the mechanisms of damage to the auditory system due to smoke inhalation and exposure are unclear, Dr. Katbanma hypothesizes that the following occurs whenever someone smokes a cigarette:
1. Nicotine and carbon monoxide deplete oxygen levels to the cochlea, which is suffused with blood. In this mechanism, damage occurs by hypoxia (or lack of oxygen) to the hair cells.
2. The neurotransmitters that convey sensory information along the auditory nerve to the brain are disrupted by nicotine, limiting their function.
3. The auditory nerve is not fully developed until late adolescence, which means that secondhand smoking puts adolescents at increased risk for hearing impairment (corroborated by the 2013 study mentioned above).
Again, while the link between smoking and hearing loss has not been clearly established, the mounting evidence indicates that smoking does more harm than good when it comes to hearing. Yet another reason to encourage friends and loved ones to kick the habit!