Study links smoking to higher risk of hearing loss

Smoking, a well-known risk factor for cancer and heart disease, also may play a role in hearing loss. A new study by researchers at the UW Medical School suggests that those who smoke are more than one and a half times as likely to have a hearing loss as nonsmokers.

The findings, reported in the June 3 issue of the Journal of the American Medical Assocation, are based on a five-year study of 3,753 middle-aged and older adults in Beaver Dam, Wisconsin.

Beaver Dam (the city and township include a population of about 20,000) is an agricultural/industrial community about 40 miles northeast of Madison and is known to researchers worldwide. It is the site of one of the largest population-based studies ever conducted on vision and factors that might affect vision loss. Now the same can be said for hearing.

The latest research was led by Karen Cruickshanks, UW Medical School associate professor of ophthalmology and visual sciences, and funded by the National Institute on Aging. Participants in the study completed several detailed questionnaires followed by a standardized battery of tests that measured hearing frequencies with pure tone audiometry. Hearing loss was defined as an average loss of more than 25 decibels compared with normal hearing. People with this mild form of hearing loss would have some difficulty understanding conversation when there’s background noise.

After accounting for several factors (age, occupational noise exposure, history of cardiovascular disease and education), Cruickshanks’ research team found that smokers were, as a group, 1.7 times as likely to have a hearing loss as nonsmokers. The more people smoked, the greater their odds of developing at least a mild hearing loss. For example, smokers who went through an average of a pack a day for 40 years were 1.3 times as likely to have a hearing loss as smokers who had smoked a pack a day for a decade.

Cruickshanks emphasized that the research suggests an association between smoking and hearing loss, but more study is needed to determine if a direct cause and effect relationship exists. She is now in the early stage of that research; findings from smaller, previous studies have not been consistent. Some have speculated that cigarette smoke has a toxic effect on cells in the inner ear which are important for hearing. Others suspect that smoking constricts blood flow to the inner ear, just as smoking cuts off blood supply to the heart and causes heart disease.

The study is the second to come out of Beaver Dam which links smoking to sensory loss. Drs. Ronald and Barbara Klein, the principal investigators of the Beaver Dam Eye Study and professors of ophthalmology and visual sciences at UW Medical School, have published research indicating that cigarette smokers have two to three times the risk of age-related macular degeneration (AMD) as nonsmokers. AMD is a leading cause of blindness.

“All of this information is useful in providing another important reason to quit smoking or, better yet, not start,” says Ronald Klein. “Age-related macular degeneration and hearing loss become more frequent as people get older. For this reason, identifying possible causes of these age-related conditions may improve quality of life.”