Association Between Retinal Pathology and Hearing in Older Adults

Abstract We investigated the association between retinal microvascular changes and hearing loss based on the hypothesis that both may result from shared microvascular pathology. Data from 536 older adults from the National Health and Nutritional Examination Survey 2005 to 2006 including sociodemographic and health characteristics, pure‐tone hearing thresholds, and retinal pathologies were collected and analyzed. Associations between retinal and hearing pathologies were modeled with multivariable‐adjusted linear regressions. 75% of participants had hearing loss and 15% of participants had retinopathy. The association between retinopathy, microaneurysms, and blot hemorrhages with better speech‐frequency pure tone average was −2.81 (95% confidence interval [CI]: −5.72 to 0.10), −4.75 (95% CI: −8.73 to −0.78), and −5.34 (95% CI: −8.68 to −2.00), respectively. The presence of retinopathy, microaneurysms, and blot hemorrhages was inversely associated with hearing loss. Further studies are needed to better understand the potential relationship between microvascular pathologies of the eye and ear.

A ge-related hearing loss is prevalent and associated with several adverse health outcomes, [1][2][3][4] including cognitive decline. 5Vascular pathologies could contribute to hearing loss through impaired cochlear blood supply. 6][9][10] The retinal microvasculature, however, can be imaged noninvasively to measure changes in cerebral microvasculature, [11][12][13][14] changes that we hypothesize could apply to the enshrouded cochlear microvasculature.In this study, we use a nationally representative sample from the National Health and Nutritional Examination Survey (NHANES) to investigate the association between retinal microvascular changes and hearing loss based on the hypothesis that both result from shared microvascular pathology.

Methods
Adults aged ≥70 years from the 2005 to 2006 cycle of NHANES were studied.Pure-tone hearing thresholds in decibels (dB) hearing level were averaged to create speechfrequency (0.5-4 kHz), low-frequency (0.5-2 kHz), and high-frequency (4-8 kHz) pure-tone averages (PTAs) in the worse-hearing ear, with greater values indicating worse hearing.Hearing loss was defined as PTA>25 dB in the worse hearing ear.The presence of retinal pathologies, including retinopathy, arteriovenous nicking, focal arteriolar narrowing, microaneurysms, and blot hemorrhages for the worse-seeing eye, were identified from graded fundus photographs.Sociodemographic characteristics, including age, sex, race, education, smoking history, and occupational exposure to loud noise, were collected in addition to health characteristics, including hypertension, diabetes, stroke, and body mass index.
Means and standard deviations or frequencies and percentages of demographics and health characteristics were examined.Multivariable-adjusted linear regression was used to model the associations and was stratified by diabetes status.A 2-sided P < .05 was considered statistically significant.Statistical analyses were conducted using Stata version 17.0 (StataCorp LLC).The study protocol was approved by the National Center for Health Statistics Institutional Review Board; all participants provided written informed consent.

Results
The final sample comprised 536 participants (Figure 1, Table 1).The prevalence of hearing loss was 402 536 (75.0%), and the mean speech-frequency PTA was 37.4 dB HL (standard deviation: 15.3) in the worse-hearing ear.The presence of retinal pathology ranged from 4.1% (focal arteriolar narrowing) to 17.9% (arteriovenous nicking).Participant characteristics by retinopathy in the worse eye are described in Supplemental Table S1, available online.While 81 536 participants (15.1%) had retinopathy, the distributions of speech-frequency, low-frequency, and high-frequency PTAs were similar between those with and without retinopathy.

Discussion
This study found an association of retinopathy, microaneurysms, and blot hemorrhages with better hearing; in other words, more retinal pathologies were associated with less hearing loss.This association was significant for  low-frequency PTA across all 3 retinal pathologies and borderline for the association between retinopathy and speech-frequency PTA.This seemed to occur regardless of the presence of diabetes.Interestingly, there were no significant associations between retinal pathology and better high-frequency PTA.In those without diabetes, however, focal arteriolar narrowing was associated with worse high-frequency PTA.This study adds to the small body of literature investigating the relationship between retinal microvascular abnormalities and hearing loss.In the Blue Mountains hearing study, Liew et al performed retinal photography and PTA on individuals aged 54 and older.They found an association between retinopathy and lowfrequency hearing loss in women only. 15More recently, Kim et al studied patients aged 45 to 64 and found that retinopathy was significantly associated with better rather than worse higher-frequency hearing. 16The difference in findings between our study and prior studies may be attributed to differences in the demographics of our cohort.8][19] Our relatively healthier population of adults 70 years and older showed a high incidence of hearing loss but a lower incidence of other comorbidities, whereas 75% of participants had hearing loss, only 25% had diabetes, and less than 20% had retinal pathology.The degree of retinal and, thus, microvascular pathology in our cohort may have been milder than in previously studied cohorts, preventing our ability to support the hypothesis of a common microvascular pathology contributing to both retinal disease and hearing loss. 20lternatively, the inverse association between retinal pathologies and low-and speech-frequency hearing loss identified here suggests a potential protective relationship between the visual and auditory systems, where the impairment of one system is associated with better performance in the other system.
Recent studies have found an association between metformin, a medication commonly used to treat diabetes, and reduced risk of sensorineural hearing loss. 21We found, however, protective relationships in the groups with and without diabetes.Future studies can help further elucidate whether this type of sensory compensation can occur later in life. 22

Conclusion
We found an inverse association between retinopathy, microaneurysms, and blot hemorrhages with hearing loss, adding to the literature examining the association between retinal abnormalities and hearing loss in older adults.Further epidemiologic studies are needed to understand better the potential relationship between microvascular pathologies of the eye and ear.

Author Contributions
Zahra N. Sayyid, analyzed data and wrote the initial manuscript draft; Armaan F. Akbar, analyzed data and wrote the initial manuscript draft; Kening Jiang, designed the study and analyzed data; Jacob M. Pogson, designed the study; Nicholas S.

Figure 1 .
Figure 1.Flow chart of selection of study participants.NHANES, National Health and Nutritional Examination Survey.

Table 2 .
Multivariable-Adjusted Linear Models for Speech-FrequeNcy, Low-Frequency, and High-frequency PTAs in Worse-Hearing Ear by Retinal Signs in Worse Eye, Stratified by Diabetes Status