The Effect of Hearing Aid Use on the Association Between Hearing Loss and Brain Structure in Older Adults.

OBJECTIVES: Recent studies have shown an association between poorer hearing thresholds and smaller brain tissue volumes in older adults. Several underlying causal mechanisms have been opted, with a sensory deprivation hypothesis as one of the most prominent. If hearing deprivation would lead to less brain volume, hearing aids could be hypothesized to moderate this pathway by restoration of hearing. This study aims to investigate whether such a moderating effect of hearing aids exists. DESIGN: The authors conducted a cross-sectional study involving aging participants of the population-based Rotterdam Study. Hearing aid use was assessed by interview and hearing loss was quantified using pure-tone audiometry. Total brain volume, gray matter and white matter volume and white matter integrity [fractional anisotropy (FA) and mean diffusivity] were measured using magnetic resonance imaging. Only participants with a pure tone average at 1, 2, and 4 kHz (PTA1,2,4) of ≥35 dB HL were included. Associations of hearing loss with brain volume and global measures of white matter integrity were analyzed using linear regression, with hearing aid use and interaction between hearing aid use and PTA1,2,4 included as independent variables. Models were adjusted for age, sex, time between audiometry and magnetic resonance imaging, level of education, and cardiovascular risk factors. RESULTS: Out of 459 included participants with mean age (range) 70.4 (52 to 92) 41% were female. Distributions of age and sex among hearing aid users (n = 172) did not significantly differ from those without hearing aids. PTA1,2,4 was associated with lower FA, but not with a difference in total brain volume, gray matter volume, white matter volume, or mean diffusivity. Interaction between hearing aid use and PTA1,2,4 was not associated with FA or any of the other outcome measures. Additional analysis revealed that interaction between hearing aid use and age was associated with lower FA. CONCLUSIONS: We found no evidence for a moderating effect of hearing aids on the relationship between hearing loss and brain structure in a population of older adults. However, use of hearing aids did appear as an effect modifier in the association between age and white matter integrity. Future longitudinal research is needed to clarify these results.

Hearing loss and microstructural integrity of the brain in a dementia-free older population.

INTRODUCTION: As hearing loss has been identified as an important risk factor for dementia, we aimed to assess the association between hearing loss and microstructural integrity of the brain. METHODS: A total of 1086 dementia-free participants (mean age = 75.2 [standard deviation: 4.9], 61.4% female) of the population-based Atherosclerosis Risk in Communities (ARIC) study underwent hearing assessment (2016-2017) and magnetic resonance imaging of the brain (2011-2013). Microstructural integrity was determined with diffusion tensor imaging. Multivariable linear regression was used to investigate associations between hearing loss and microstructural integrity of different brain regions and white matter (WM) tracts. RESULTS: Hearing loss was associated with lower WM microstructural integrity in the temporal lobe, lower gray matter integrity of the hippocampus, and with lower WM microstructural integrity of the limbic tracts and the uncinate fasciculus. CONCLUSION: Our results demonstrate that hearing loss is indepedently associated with lower microstructural integrity in brain regions that are important for different cognitive processes.

Progression of Hearing Loss in the Aging Population: Repeated Auditory Measurements in the Rotterdam Study.

We quantified changes in the auditory acuity of 675 aging adults (mean age 71.1 years, 52.0% female, mean follow-up 4.4 years ± 0.2) of an ongoing cohort study with a pure-tone audiogram and a speech-in-noise test. Generalized estimating equation models were used to study the association between hearing loss and the progression with age, sex, education, cognition, BMI, blood pressure, having type 2 diabetes mellitus, cholesterol ratio, smoking and alcohol consumption. The mean progression of hearing loss was 0.29 and 1.35 dB/year (low and high frequencies). Progression of hearing loss was associated with baseline hearing thresholds. Besides, the presence of type 2 diabetes, smoking, age, sex and time were associated with worse hearing at baseline, but there was no statistical evidence that the tested determinants were associated with progression of hearing loss. This finding indicates that the 4-year progression of hearing loss in older adults in this study is not influenced by the measured determinants. More research with multiple follow-up rounds is desired.

White-matter microstructure and hearing acuity in older adults: a population-based cross-sectional DTI study.

To study the relation between the microstructure of white matter in the brain and hearing function in older adults we carried out a population-based, cross-sectional study. In 2562 participants of the Rotterdam Study, we conducted diffusion tensor imaging to determine the microstructure of the white-matter tracts. We performed pure-tone audiogram and digit-in-noise tests to quantify hearing acuity. Poorer white-matter microstructure, especially in the association tracts, was related to poorer hearing acuity. After differentiating the separate white-matter tracts in the left and right hemisphere, poorer white-matter microstructure in the right superior longitudinal fasciculus and the right uncinate fasciculus remained significantly associated with worse hearing. These associations did not significantly differ between middle-aged (51-69 years old) and older (70-100 years old) participants. Progressing age was thus not found to be an effect modifier. In a voxel-based analysis no voxels in the white matter were significantly associated with hearing impairment.

Corrigendum: Hearing Impairment Is Associated with Smaller Brain Volume in Aging.

[This corrects the article on p. 2 in vol. 9, PMID: 28163683.].

Hearing Impairment Is Associated with Smaller Brain Volume in Aging.

Although recent studies show that age-related hearing impairment is associated with cerebral changes, data from a population perspective are still lacking. Therefore, we studied the relation between hearing impairment and brain volume in a large elderly cohort. From the population-based Rotterdam Study, 2,908 participants (mean age 65 years, 56% female) underwent a pure-tone audiogram to quantify hearing impairment. By performing MR imaging of the brain we quantified global and regional brain tissue volumes (total brain volume, gray matter volume, white matter (WM) volume, and lobe-specific volumes). We used multiple linear regression models, adjusting for age, sex, head size, time between hearing test and MR imaging, and relevant cognitive and cardiovascular covariates. Furthermore, we performed voxel-based morphometry to explore sub-regional differences. We found that a higher pure-tone threshold was associated with a smaller total brain volume [difference in standardized brain volume per decibel increase in hearing threshold in the age-sex adjusted model: -0.003 (95% confidence interval -0.004; -0.001)]. Specifically, WM volume was associated. Both associations were more pronounced in the lower frequencies. All associations were consistently present in all brain lobes in the lower frequencies and in most lobes in the higher frequencies, and were independent of cognitive function and cardiovascular risk factors. In voxel-based analyses we found associations of hearing impairment with smaller white volumes and some smaller and larger gray volumes, yet these were statistically non-significant. Our findings demonstrate that hearing impairment in elderly is related to smaller total brain volume, independent of cognition and cardiovascular risk factors. This mainly seems to be driven by smaller WM volume, throughout the brain.

Contributing Determinants to Hearing Loss in Elderly Men and Women: Results from the Population-Based Rotterdam Study.

To contribute to a better understanding of the etiology in age-related hearing loss, we carried out a cross-sectional study of 3,315 participants (aged 52-99 years) in the Rotterdam Study, to analyze both low- and high-frequency hearing loss in men and women. Hearing thresholds with pure-tone audiometry were obtained, and other detailed information on a large number of possible determinants was collected. Hearing loss was associated with age, education, systolic blood pressure, diabetes mellitus, body mass index, smoking and alcohol consumption (inverse correlation). Remarkably, different associations were found for low- and high-frequency loss, as well as between men and women, suggesting that different mechanisms are involved in the etiology of age-related hearing loss.