The prevalence of hearing impairment* in adults 65–74 years old is lower now than it was 40 years ago, according to an NIDCD-funded study published in the May 2012 issue of Ear and Hearing. The findings are consistent with the researchers’ earlier discovery that younger adults are hearing much better than their grandparents did at their age.
The new study analyzed audiometric data (hearing tests) collected in 1999–2006 and compared them to similar data for adults 65-74 years of age collected 40 years earlier in 1959–1962. Hearing impairment in adults in this age group dropped from 48 percent in 1959–1962 to 36 percent in 1999–2006. Hence, the researchers concluded the rate of hearing impairment for adults who are currently 65–74 years of age is 25 percent better than it was for adults of the same age 40 years ago.
"It’s difficult to explain why this decrease in hearing impairment occurred, since the two age groups we looked at were born in the decades circa 1890 and 1930,” said Howard Hoffman, NIDCD epidemiologist and lead author of the paper. "They became adults before the general availability of antibiotics to treat childhood ear infections or the widespread introduction of vaccines, which have since greatly reduced the incidence of common childhood diseases such as measles and mumps that may result in permanent hearing loss.”
The researchers suggest instead that the improvement in hearing may owe less to advances in medical treatments, and more to incremental advances made in public health (for example, sanitation and safer and healthier foods), education, and transportation in the first half of the twentieth century.
More specific reasons for the improvement may include safer working conditions, fewer noisy jobs and more use of hearing protection, less smoking, better control of infectious diseases and, more recently, improved control of diabetes and other cardiovascular risk factors.
*Hearing impairment is based on the World Health Organization's (WHO) standard definition, which defines adult hearing impairment as a four frequency average of hearing thresholds (measured at 500, 1000, 2000, and 4000 Hertz) that exceeds 25 decibels (dB) hearing level in the ear with better hearing.