One in 10 adults ages 45 to 54 had a hearing impairment, a large cohort study showed, and some of the risk factors are modifiable.
Among more than 2,800 adults with an average age of 49, 14.1% had hearing impairment, according to Scott Nash, MS, a doctoral student at the University of Wisconsin School of Medicine and Public Health in Madison, and colleagues.
The prevalence increased steadily from 2.9% in those ages 21 to 34 to 42.7% in those ages 65 to 84, and was consistently higher in males than females, the researchers reported online in Archives of Otolaryngology — Head & Neck Surgery.
They identified some modifiable risk factors that were associated with the odds of hearing impairment, including central retinal venular equivalent, hematocrit percentage, statin use, and mean intima-media thickness.
The findings suggest “that hearing impairment, if detected early, may be a preventable chronic disease,” Nash and his colleagues wrote.
The researchers examined data from the Beaver Dam Offspring Study, an epidemiological cohort study of aging that included the children of participants in the population-based Epidemiology of Hearing Loss Study conducted in Wisconsin.
The analysis included 2,837 individuals who underwent a hearing examination, which included otoscopy, tympanometry, pure-tone air- and bone-conduction audiometry, and a test of word recognition both with a quiet background and with another person talking.
The pure-tone average was calculated using the thresholds from the 0.5, 1.0, 2.0, and 4.0 kHz frequencies. Hearing impairment was defined as a pure-tone average greater than 25 dB hearing level in either ear.
The mean percentage of words identified correctly on the recognition test when there was a competing voice in the background was 64%.
In a multivariate model, the following factors were independently and significantly associated with hearing impairment:
- History of ear surgery, OR 4.11
- Male gender, OR 3.80
- Less education (12 or fewer years), OR 1.79
- Larger central retinal venular equivalent (fourth versus first quartile), OR 1.77
- Age (per 5 years), OR 1.70
- Noisy job, OR 1.57
- Higher hematocrit percentage (per 5%), OR 0.77
Factors associated with a lower score on the word recognition test were similar, with the addition of increased intima-media thickness and statin use (P=0.005 for both).
Central retinal venular equivalent and hematocrit could be considered risk factors for cardiovascular disease along with intima-media thickness and statin use, according to the researchers.
“These results suggest that there may be cardiovascular antecedents of hearing impairment, as measured by pure-tone or speech audiometry, which are detectable even in middle age,” they wrote.
They noted that the finding that increasing hematocrit was associated with a lower chance of hearing impairment was opposite what would be expected because of its proposed correlation with blood viscosity, which has been associated with higher blood pressure and greater risk of ischemic heart disease.
Nash and his colleagues proposed some explanations for the apparent discrepancy.
First, they wrote, hematocrit may be an imperfect surrogate for blood viscosity.
Second, the blood vessels may be less athersclerotic in younger adults and thus more resistant to the negative effects of increasing blood viscosity.
And finally, hematocrit in younger adults may be more a reflection of diet or vitamin use.
The authors acknowledged some limitations of the study, including the cross-sectional design, which precludes the establishment of causal relationships, the possibility that some of the associations were attributable to type 1 errors, and the fact that more of the participants had a history of parental hearing loss than nonparticipants.