Abstract
The present study examined auditory function across age in the dark agouti (DA) rat strain. Auditory brainstem responses (ABRs) were measured for frequencies 8, 16, and 32 kHz in male and female DA rats from 3 to 18 months of age. Hearing thresholds and absolute and interpeak latencies (IPLs) were analyzed. Male hearing thresholds remained stable for the first year of life and then significantly increased at 18 months across all frequencies; female hearing remained stable at all tested ages out to 18 months. At 12 months, male DA rats showed significantly longer absolute latencies by age (i.e., compared with 3-month-old males) and sex (compared with 12-month-old females), with no differences in IPLs. At 18 months, female DA rats showed significantly longer absolute latencies with age (compared with 3-month-old females) and sex (compared with 18-month-old males), particularly for the later waves. Female IPLs were also significantly longer with age and by sex for the later waves. This report supports the feasibility of using male DA rats in studies to investigate age-related hearing loss (ARHL; presbycusis).
Highlights
Hearing loss is the third most common chronic disability and surveys by the Centers for Disease Control and Prevention (CDC, Atlanta, GA) reveal that it currently affects 16% of U.S adults aged 18 and over [1]
There is a tremendous financial burden associated with hearing loss; in 2017, the World Health Organization predicted that the annual cost of unaddressed hearing loss will reach $790 billion globally [2]
The number of people affected with hearing loss is expected to continuously rise; data from the National Health and Nutrition Examination Survey predict an increase from 44.1 million Americans in 2020 to 73.5 million Americans in 2060 [4]
Summary
Hearing loss is the third most common chronic disability and surveys by the Centers for Disease Control and Prevention (CDC, Atlanta, GA) reveal that it currently affects 16% of U.S adults aged 18 and over [1]. One of the major causes of hearing loss is from the normal aging process, i.e., presbycusis, characterized by reduced hearing sensitivity from age-related deterioration of inner ear sensory cell, vascular and neural function [3]. The number of people affected with hearing loss is expected to continuously rise; data from the National Health and Nutrition Examination Survey predict an increase from 44.1 million Americans in 2020 to 73.5 million Americans in 2060 [4]. Hearing impairment has been identified at earlier ages in men than women, decline in hearing sensitivity occurs twice as fast for men, and hearing thresholds in elderly men were identified to be higher than elderly women [5,6]
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