Age-related hearing loss (HL) is a highly prevalent and undertreated disease that has long been considered an inconsequential result of aging, and at worst, a simple quality of life problem. Recent research suggests that HL may have significant implications for mental and neurocognitive health. Several studies have shown preliminary evidence associating HL and depression.1 Identifying modifiable risk factors for late-life depression is crucial because depression is relatively common and disabling in the elderly. Late-life depression is often resistant to medications such as antidepressants. Since HL is highly prevalent, severely undertreated, easily diagnosed, and treatable (by hearing aids or cochlear implants), establishing a link between HL and late-life depression may yield a strategy to prevent or treat depression in the sub-group of patients who also have HL.
A recent study2 by our team investigated whether an association between audiogram-measured HL and clinically significant depressive symptoms exists by using data from the Hispanic Community Health Study/Study of Latinos (HCHS). Determining whether this association exists in a racial/ethnic minority, such as the Hispanic population, was of specific interest for several reasons. Depression has been reported to be more common in the Hispanic population compared to other ethnic/racial groups.3 In addition, depression may be underdiagnosed in Hispanic individuals due to language, cultural, and literacy barriers to health care.4 Moreover, early studies evaluating this association have largely been limited to Caucasian cohorts.1 A finding in one race/ethnic group does not necessarily translate to another.
The HCHS is a multicenter, prospective, community-based cohort study of Hispanic/Latino adults in the United States. This dataset includes information from audiograms, interviews, physical examinations, and tests, such as laboratory bloodwork and neuropsychological testing. This cohort also happens to have a large sample of Hispanic individuals with audiometric hearing data—in fact, the largest study to date (5,328 subjects compared with 1,332 in the previously largest study5). Importantly, this dataset included a measure of depressive symptoms known as the Center for Epidemiologic Studies Depression Scale, 10-item version (CESD-10, a 10-question yes/no survey). Data collected from a total of 5,328 individuals were included in the study after excluding data on those below 50 years old and those with early-onset hearing loss or missing key data, such as audiograms, CESD-10 scores, or demographics.
In this cross-sectional study, hearing loss was assessed using pure-tone audiometry in soundproof booths. All individuals had pure-tone audiometry across frequencies 500 Hz to 8,000 Hz tested by trained technicians. The four-frequency pure-tone average (PTA) based on hearing thresholds at 500, 1,000, 2,000, and 4,000 Hz was calculated for each ear; HL was based on the PTA of the better ear, and unilateral HL was excluded. Severity of HL was categorized as follows: absent or normal, 0 to 25 dB; mild 26 to 40 dB; moderate, 41 to 55 dB; moderately severe, 56 to 70 dB; severe 71 to 90 dB; and profound, 91 dB or greater.2 Since few participants had severe or profound HL, individuals in these categories were combined with those in the moderately severe HL group to form a category of moderately severe or worse (56 dB or greater) HL.
Depressive symptoms were measured using the CESD-10. Examples of questions include “I felt depressed” and “I felt that everything I did was an effort.” Clinically significant depressive symptoms were defined by a CESD-10 score of 10 or higher, a cutoff also used in prior research.6 The study also adjusted for other variables that may confound the association between HL and depression. By confound, we mean that these variables might create a seemingly false association between HL and depressive symptoms. For example, age can cause both HL and depression. By adjusting for age, we take this into account to reduce or eliminate the confounding effect of age. These other variables were adjusted for included use of hearing aids, demographics (age, sex, educational level, etc.), and cardiovascular disease.
Baseline participant characteristics listed by HL category are provided in Table 1. The median age of participants was 58 years old. Of the 5,328 participants, 62 percent were women. Most patients (82%) had no HL, 14 percent had mild HL, 2.7 percent had moderate HL, and 0.9 percent had moderately severe or worse HL. The mean CESD-10 score was 7.7. Clinically significant depressive symptoms (i.e., a CESD-10 score ≥10) were present in 32 percent of participants without HL, 34 percent with mild HL, 45 percent with moderate HL, and 57 percent with moderately severe or worse HL.
When adjusting for other variables that might cause confounding, such as hearing aid use, demographic factors, cardiovascular disease, and antidepressants, the odds of clinically significant depressive symptoms (CESD-10 score ≥10) increased 1.44 times for every 20 dB increase in HL. This adjusted model was used to calculate the odds of clinically significant depressive symptoms in each category of HL compared to normal hearing (0 dB hearing loss; Table 2). The odds of clinically significant depressive symptoms were 1.81 times as high for mild HL, 2.38 times as high for moderate HL, 3.12 times as high for moderately severe HL, and 4.30 times as high for severe HL.
The association between HL and depression, both common conditions of older life, was not previously well established. This study shows a strong association between audiometric HL and clinically significant depressive symptoms using a large Hispanic study population. When accounting for hearing aid use, age, sex, educational level, study site, geographic background, cardiovascular disease, and antidepressant use, the odds of having clinically significant depressive symptoms increased nearly 1.5 times for every additional 20 dB of HL. This is clinically significant, as 20 dB is approximately the difference between each category of HL; for example, moderate (41-55 dB) vs. mild (26-40 dB) HL. An individual with mild HL had almost twice the odds of having clinically significant depressive symptoms compared with someone with normal hearing (0 dB HL). An individual with moderate HL had nearly 2.5 times the odds and an individual with severe HL had over four times the odds of having clinically significant depressive symptoms.
It is intuitive to hypothesize that HL may increase the risk for depression via the development of social isolation and loneliness, which themselves are associated with a higher risk of depression. HL treatments have been shown to improve loneliness,7 as well as social function and depressive symptoms.8 However, a key limitation of the study is that it does not prove that HL causes depression. This study was a cross-sectional, observational study that shows an association between HL and depression. As we know, association is not the same as causation; only a randomized controlled trial could show causation.
This study adds to the growing literature examining HL and depression. It provides a more robust statistical analysis, includes data from multiple sites across the country, and is the largest to date examining HL and depression. The study also extends earlier findings9 to a different ethnic group. Given that the Hispanic population is the fastest growing ethnicity in the United States and depression may be more prevalent in this population compared to other ethnic/racial groups,3 identifying modifiable risk factors for depression in Hispanic/Latino individuals is crucial. This is especially important because Latino individuals are less likely to start medical (antidepressant) therapy and more likely to discontinue such therapy within the first 30 days of treatment.10
Depression in later life is a heterogeneous disorder with many risk factors, and results from this study suggest that HL may be one important pathway to becoming depressed. The high prevalence (80% in individuals older than 80 years of age) and infrequent treatment (<20% use hearing aids or cochlear implants) of HL amongst the elderly implies that recognizing and treating HL may have the potential to significantly improve health outcomes for older adults. While we don't know whether HL causes depression, nor do we know whether treating HL will prevent depression, it seems very reasonable to recommend treatment for older adults with HL given the low risk of hearing aid use and broad potential benefit. Future longitudinal studies and randomized controlled trials examining whether treating HL reduces the risk of late-life depression can help elucidate the relationship between HL and depression. Establishing a causal link between HL and depression may eventually guide clinical practice guidelines and treatment recommendations regarding HL as a modifiable risk factor for depression.
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