Arteriolar sclerosis as a cause of presbycusis

Association Between Metabolic Syndrome and Hearing Impairment: a Study on 200 Subjects

The metabolic syndrome (MS) is a cluster of conditions that occur. togehther, increase risk of heart disease, storke, type 2 diabetes mellitus and hypertension as a possible outcome. The previous research has shown a link between hearing loss and being overweight, diabetic, or suffering from heart disease. However, research on the possible link between hearing loss and metabolic syndrome is limited. Hearing loss due to metabolic syndrome was evaluated in the present investigation. Two hundred individuals with metabolic syndrome were included. All the patients were evaluated on three types of audiometry (pure tone, impedence, and DPOAE).Anthropometric data, blood pressure, blood sugar, and lipid profiles, were all collected from each patient. We also asked about their smoking and drinking habits in the past. SPSS v. 22.0 was used to conduct the statistical analysis. Overall, SNHL affected 58.5% of patients. Patients having moderate hearing loss were the largest demographic group (40%), followed by those with mild hearing loss (15% ). Severe hearing loss only occurred in 3.5% of patients. Hearing loss was shown to be more prevalent in patients with more than three components of metabolic syndrome. Significant associations were found between hearing impairment and metabolic risk factors as waist circumference, fasting blood sugar, serum high-density lipoprotein, serum triglycerides, and systolic and diastolic blood pressure. Hearing loss was only marginally connected to smoking and excessive drinking.

Obesity and risk of hearing loss in the middle-aged and elderly: a national cohort of Chinese adults

BACKGROUND

The relationship between obesity and hearing loss among the middle-aged and older population remained unclear. Moreover, few studies have focused on the impact of gender on this association.

METHODS

This cohort study extracted the data from the China Health and Retirement Longitudinal Study, a national survey of adults aged 45 years or over. Waist circumference was categorized into three groups: normal, pre-central obesity, and central obesity. We classified BMI into four categories: underweight, normal weight, overweight, and obese. The primary endpoint was the incidence of self-reported hearing loss.

RESULTS

Of the 14,237 participants, 1972 incidents of hearing loss were identified during a median 6.9 years of follow-up. The cumulative incidence of hearing loss was 13.9% (95% CI 13.3% -14.4%). Our study showed that central obesity was significantly associated with hearing loss (HR 0.84, 95%CI 0.75-0.94), and this relationship was more prominent in males (HR 0.76, 95%CI 0.63-0.91). Among male participants, the underweight group was at the highest risk of hearing loss (HR 1.39, 95%CI 1.08-1.79). Compared with the normal weight group, the adjusted HR for hearing loss in the obese groups was 0.69 (95%CI 0.51-0.94) among men. Among female participants, only the overweight group had a lower risk of hearing loss than the normal weight group (HR 0.83, 95%CI 0.71-0.96).

CONCLUSIONS

Being overweight and obese were significantly associated with a decreased risk of hearing loss, whereas being underweight was associated with an increased risk of hearing loss.

Probability Distributions for Associations Between Cognitive Screening and Pure-tone Thresholds in Older Adults

OBJECTIVES

Lower general cognitive function is frequently reported in older adults with elevated pure-tone thresholds. Here, we examined reason(s) for this association, including whether this relationship is dependent on the frequency range or extent of hearing loss and cognitive screening performance.

DESIGN

Linear regression was used to examine associations between better-ear pure-tone thresholds and Mini-Mental Status Exam (MMSE) performance in a cross-sectional sample of relatively healthy older adults (N = 508; 68% women, 60-89+ years; M age = 72). Quantile regression was also used to identify the ranges of 0.5 and 4.0 kHz thresholds and MMSE scores where these variables exhibited significant associations.

RESULTS

MMSE scores and pure-tone thresholds exhibited small but significant associations, particularly for better-ear 0.5 kHz thresholds. This hearing threshold and cognitive screening association was present among participants with better hearing, including the oldest older adults. There was limited evidence for mediating health condition effects on this association. An item analysis of the MMSE revealed that the MMSE and pure-tone threshold associations were largely due to the delayed recall item of the MMSE.

CONCLUSIONS

Together, the small effect results are consistent with the extant literature and suggest that there are multiple reasons for modest pure-tone threshold and cognitive screening performance associations.

Association of Body Mass Index with Hearing Loss in Korean Adult Population

This study aimed to explore the relationship between body mass index (BMI) and hearing loss. We analyzed data from the Korean National Health Insurance Service Health Screening Cohort 2009−2019 (291,471 patients with hearing loss and 6,088,979 control participants). Both patient groups were subsequently divided into four groups according to BMI: <18.5 (underweight), 18.5−24.9 (normal), 25−29.9 (obese I), and ≥30 (obese II). To evaluate the relationship between BMI and hearing loss, multivariate logistic regression analysis was used, adjusting for age, sex, smoking, alcohol consumption, blood pressure, triglycerides, total cholesterol, low-density lipoprotein, proteinuria, serum creatinine, aspartate aminotransferase, alanine aminotransferase, and fasting glucose levels. The adjusted odds ratio (OR) of the underweight group for hearing loss was 1.21 (95% CI = 1.19−1.24) compared to the normal BMI group, whereas the adjusted ORs of obese I and obese II groups for hearing loss were 0.95 and 0.87, respectively. Being underweight was generally associated with an increased prevalence of hearing loss in the Korean adult population.

Association between high systolic blood pressure and objective hearing impairment among Japanese adults: a facility-based retrospective cohort study

This retrospective longitudinal study examined the association between systolic blood pressure and hearing impairment among 13,187 Japanese individuals (men, 46.5%) aged 20-59 years. The systolic blood pressure of participants was categorized as <120, 120-129, 130-139, 140-149, 150-159, and ≥160 mmHg. Using pure-tone audiometry, hearing impairment at 1 and 4 kHz was defined as hearing thresholds in either ear >30 and >40 dB, respectively. We performed multivariable Cox proportional-hazards regression analysis to examine the association using two multiple-imputation methods (fully conditional specification and Markov chain Monte Carlo). There were 695 and 774 hearing-impairment cases at 1 and 4 kHz, respectively, during ~77,000 person-years of follow-up. Compared with the <120 mmHg group, the hazard ratios (95% confidence intervals) of hearing impairment for the 120-129, 130-139, 140-149, 150-159, and ≥160 mmHg groups after adjustment for age, sex, body mass index, high serum glucose, current smoking, and other potential confounders were 1.35 (1.12-1.63), 1.45 (1.13-1.86), 1.07 (0.73-1.58), 1.91 (1.18-3.07), and 1.81 (1.01-3.25), respectively, at 1 kHz using the first imputation method; 1.36 (1.13-1.63), 1.48 (1.17-1.86), 1.09 (0.76-1.58), 1.99 (1.29-3.06), and 1.92 (1.08-3.41), respectively, at 1 kHz using the second imputation method; 1.04 (0.86-1.24), 1.14 (0.91-1.43), 1.13 (0.83-1.54), 1.45 (0.96-2.19), and 1.35 (0.82-2.23), respectively, at 4 kHz using the first imputation method; and 1.03 (0.86-1.24), 1.17 (0.95-1.44), 1.15 (0.87-1.53), 1.54 (1.06-2.24), and 1.44 (0.88-2.35), respectively, at 4 kHz using the second imputation method. In conclusion, higher systolic blood pressure was associated with hearing impairment at 1 kHz. No clear association was observed at 4 kHz.

Age-related hearing loss and cognitive decline: MRI and cellular evidence

Extensive evidence supports the association between age-related hearing loss (ARHL) and cognitive decline. It is, however, unknown whether a causal relationship exists between these two, or whether they both result from shared mechanisms. This paper intends to study this relationship through a comprehensive review of MRI findings as well as evidence of cellular alterations. Our review of structural MRI studies demonstrates that ARHL is independently linked to accelerated atrophy of total and regional brain volumes and reduced white matter integrity. Resting-state and task-based fMRI studies on ARHL also show changes in spontaneous neural activity and brain functional connectivity; and alterations in brain areas supporting auditory, language, cognitive, and affective processing independent of age, respectively. Although MRI findings support a causal relationship between ARHL and cognitive decline, the contribution of potential shared mechanisms should also be considered. In this regard, the review of cellular evidence indicates their role as possible common mechanisms underlying both age-related changes in hearing and cognition. Considering existing evidence, no single hypothesis can explain the link between ARHL and cognitive decline, and the contribution of both causal (i.e., the sensory hypothesis) and shared (i.e., the common cause hypothesis) mechanisms is expected.

Association between Speech Recognition in Noise and Risk Factors of Cardiovascular Disease

INTRODUCTION

Risk factors for cardiovascular disease (CVD) are associated with sensorineural hearing loss. CVD risk factors are known to cluster and interact, thereby increasing the cumulative risk for CVD. Previously, using the database of the Netherlands Longitudinal Study on Hearing (NL-SH), an association was found between a history of smoking and an increased decline in speech recognition in noise over 10 years of follow-up. Prospectively limited data are available on the association between CVD risk factors, interactions of these risk factors, and hearing loss. In this study, data from the NL-SH were used to study the association between CVD risk factors and speech recognition in noise longitudinally.

METHODS

Baseline, 5-year, and 10-year follow-up data of the NL-SH were included. The NL-SH is a web-based prospective cohort study which started in 2006. Participants were aged 18-70 years at baseline. Speech recognition in noise was determined with an online digit-triplet speech-in-noise test. In addition, participants completed online questionnaires on demographic, lifestyle, and health-related characteristics. The association of the ability to recognize speech in noise with CVD risk factors (i.e., obesity, rheumatoid arthritis [RA], hypertension, diabetes mellitus, and dyslipidemia) was analyzed longitudinally. We also analyzed the interaction between these risk factors (including age, sex, and history of smoking) and speech recognition in noise.

RESULTS

None of the CVD risk factors or interactions of 2 CVD risk factors was significantly associated with a decline in SRT over time. Obesity (p = 0.016), RA (p = 0.027), and hypertension (p = 0.044) were associated with overall higher (more unfavorable) SRTs. No overall interactions between CVD risk factors were found.

CONCLUSION

Obesity, RA, and hypertension were overall associated with a higher SRT, but no longitudinal associations between these or other CVD factors with SRTs were found. Also, no interactions between 2 CVD risk factors and SRTs were found. Although no longitudinal associations between CVD risk factors and decline in SRTs were found, clinicians should be alert about the concurrent association between CVD risk factors and hearing loss.

Betaine-homocysteine S-methyltransferase deficiency causes increased susceptibility to noise-induced hearing loss associated with plasma hyperhomocysteinemia

Betaine-homocysteine S-methyltransferases (BHMTs) are methionine cycle enzymes that remethylate homocysteine; hence, their malfunction leads to hyperhomocysteinemia. Epidemiologic and experimental studies have revealed a correlation between hyperhomocysteinemia and hearing loss. Here, we have studied the expression of methionine cycle genes in the mouse cochlea and the impact of knocking out the Bhmt gene in the auditory receptor. We evaluated age-related changes in mouse hearing by recording auditory brainstem responses before and following exposure to noise. Also, we measured cochlear cytoarchitecture, gene expression by RNA-arrays and quantitative RT-PCR, and metabolite levels in liver and plasma by HPLC. Our results indicate that there is an age-dependent strain-specific expression of methionine cycle genes in the mouse cochlea and a further regulation during the response to noise damage. Loss of Bhmt did not cause an evident impact in the hearing acuity of young mice, but it produced higher threshold shifts and poorer recovery following noise challenge. Hearing loss was associated with increased cochlear injury, outer hair cell loss, altered expression of cochlear methionine cycle genes, and hyperhomocysteinemia. Our results suggest that BHMT plays a central role in the homeostasis of cochlear methionine metabolism and that Bhmt2 up-regulation could carry out a compensatory role in cochlear protection against noise injury in the absence of BHMT.-Partearroyo, T., Murillo-Cuesta, S., Vallecillo, N., Bermúdez-Muñoz, J. M., Rodríguez-de la Rosa, L., Mandruzzato, G., Celaya, A. M., Zeisel, S. H., Pajares, M. A., Varela-Moreiras, G., Varela-Nieto, I. Betaine-homocysteine S-methyltransferase deficiency causes increased susceptibility to noise-induced hearing loss associated with plasma hyperhomocysteinemia.

Obesity and risk of hearing loss: A prospective cohort study

BACKGROUND & AIMS

The existing yet limited prospective studies reported conflicting results about obesity and hearing loss. We investigated the prospective association between obesity and hearing loss in a large-scale Japanese working population, as well as the association between metabolic phenotype and hearing loss.

METHODS

The study included 48,549 employees aged 20-64 years and free of hearing loss at baseline. Pure-tone audiometric testing was performed annually to identify hearing loss at 1 and 4 kHz. Cox proportional hazards regression was used to investigate the risk of hearing loss associated with body mass index (BMI) and metabolic phenotype (based on a BMI of ≥25.0/<25.0 kg/m² and presence/absence of ≥2 components of metabolic syndrome, except waist circumference). Baseline and updated information were obtained from annual health checkups.

RESULTS

With a median follow-up of 7 years, 1595 and 3625 individuals developed unilateral hearing loss at 1 and 4 kHz, respectively. The adjusted hazard ratios (HR) for hearing loss at 1 kHz were 1.21 (1.08, 1.36) and 1.66 (1.33, 2.08) for those with BMI 25.0-29.9 kg/m² and BMI ≥30.0 kg/m², respectively, compared to individuals with BMI <25.0 kg/m². For hearing loss at 4 kHz, the corresponding HRs were 1.14 (1.05, 1.23) and 1.29 (1.09, 1.52). Compared with metabolically healthy non-obese individuals, the adjusted HRs for hearing loss at 1 kHz were 1.19 (1.03, 1.39), 1.27 (1.01, 1.61), and 1.48 (1.25, 1.76) for unhealthy non-obese, healthy obese, and unhealthy obese individuals, respectively. For hearing loss at 4 kHz, the corresponding HRs were 1.13 (1.04, 1.25), 1.21 (1.04, 1.41), and 1.26 (1.12, 1.41).

CONCLUSIONS

Overweight and obesity are associated with an increased risk of hearing loss, and metabolically unhealthy obesity may confer additional risk.

Age-Related Hearing Loss Associations With Changes in Brain Morphology

Age-related hearing loss has been associated with varied auditory cortex morphology in human neuroimaging studies. These findings have suggested that peripheral auditory system declines cause changes in brain morphology but could also be due to latent variables that affect the auditory periphery and brain. The current longitudinal study was designed to evaluate these explanations for pure-tone threshold and brain morphology associations. Thirty adults (mean age at Time 1 = 64.12 ± 10.32 years) were studied at two time points (average duration between visits = 2.62 ± 0.81 years). Small- to medium-effect size associations were observed between high-frequency pure-tone thresholds and auditory cortex gray matter volume at each time point. Although there were significant longitudinal changes in low- and high-frequency hearing measures and brain morphology, those longitudinal changes were not significantly correlated across participants. High-frequency hearing measures at Time 1 were significantly related to more lateral ventricle expansion, such that participants with higher measures exhibited larger increases in ventricle size. This ventricle effect was statistically independent of high-frequency hearing associations with auditory cortex morphology. Together, these results indicate that there are at least two mechanisms for associations between age-related hearing loss and brain morphology. Potential explanations for a direct hearing loss effect on brain morphology, as well as latent variables that likely affect both the inner ear and brain, are discussed.

Diabetes mellitus and the incidence of hearing loss: a cohort study

Background

To evaluate the association between diabetes mellitus (DM) and the development of incident hearing loss.

Methods

Prospective cohort study was performed in 253 301 adults with normal hearing tests who participated in a regular health-screening exam between 2002 and 2014. The main exposure was the presence of DM at baseline, defined as a fasting serum glucose ≥ 126 mg/dL, a self-reported history of DM or current use of anti-diabetic medications. Pre-diabetes was defined as a fasting glucose 100-125 mg/dL and no history of DM or anti-diabetic medication use. Incident hearing loss was defined as a pure-tone average of thresholds at 0.5, 1.0 and 2.0 kHz > 25 dB in both right and left ears.

Results

During 1 285 704 person-years of follow-up (median follow-up of four years), 2817 participants developed incident hearing loss. The rate of hearing loss in participants with normal glucose levels, pre-diabetes and DM were 1.8, 3.1 and 9.2 per 1000 person-years, respectively ( P < 0.001). The multivariable-adjusted hazard ratios for incident hearing loss for participants with pre-diabetes and DM compared with those with normal glucose levels were 1.04 (95% confidence interval 0.95-1.14) and 1.36 (1.19-1.56), respectively. In spline regression analyses, the risk of incident hearing loss increased progressively with HbA1c levels above 5%.

Conclusions

In this large cohort study of young and middle-aged men and women, DM was associated with the development of bilateral hearing loss. DM patients have a moderately increased risk of future hearing loss.

Cochlear Homocysteine Metabolism at the Crossroad of Nutrition and Sensorineural Hearing Loss

Hearing loss (HL) is one of the most common causes of disability, affecting 360 million people according to the World Health Organization (WHO). HL is most frequently of sensorineural origin, being caused by the irreversible loss of hair cells and/or spiral ganglion neurons. The etiology of sensorineural HL (SNHL) is multifactorial, with genetic and environmental factors such as noise, ototoxic substances and aging playing a role. The nutritional status is central in aging disability, but the interplay between nutrition and SNHL has only recently gained attention. Dietary supplementation could therefore constitute the first step for the prevention and potential repair of hearing damage before it reaches irreversibility. In this context, different epidemiological studies have shown correlations among the nutritional condition, increased total plasma homocysteine (tHcy) and SNHL. Several human genetic rare diseases are also associated with homocysteine (Hcy) metabolism and SNHL confirming this potential link. Accordingly, rodent experimental models have provided the molecular basis to understand the observed effects. Thus, increased tHcy levels and vitamin deficiencies, such as folic acid (FA), have been linked with SNHL, whereas long-term dietary supplementation with omega-3 fatty acids improved Hcy metabolism, cell survival and hearing acuity. Furthermore, pharmacological supplementations with the anti-oxidant fumaric acid that targets Hcy metabolism also improved SNHL. Overall these results strongly suggest that cochlear Hcy metabolism is a key player in the onset and progression of SNHL, opening the way for the design of prospective nutritional therapies.

Risk Factors for Hearing Impairment among Adults with Diabetes: The Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

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Hearing impairment was experienced by 59% of adults with diabetes.

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Modifiable risk factors were smoking, high alcohol use and high triglycerides.

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Lesser education and lower income were associated with hearing impairment.

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Suboptimal glycemic control was not associated with hearing impairment.

Aim

The aim was to examine risk factors for hearing impairment among Hispanic/Latino adults with diabetes.

Methods

Findings are based on 3384 participants aged 18–76 years with diagnosed or previously undetected diabetes who completed audiometric testing as part of the Hispanic Community Health Study/Study of Latinos. We defined hearing impairment as the pure-tone average (PTA) >25 decibels hearing level [dB HL] of pure-tone thresholds at high frequencies (3000, 4000, 6000, and 8000 Hz) in the worse ear and defined a second hearing impairment outcome with the additional requirement of PTA >25 dB HL of low/mid-frequency (500, 1000, and 2000 Hz) thresholds in the worse ear. We identified independent associations using logistic regression.

Results

Controlling for age and Hispanic/Latino background, prevalence ratios for hearing impairment in the high plus low/mid frequencies were 1.35 (95% CI 1.07, 1.71) for current smoking, 1.64 (1.14, 2.38) for alcohol consumption (≥14 drinks/week for men or ≥ 7 drinks/week for women), and 1.29 (1.06, 1.56) for triglycerides ≥ 150 mg/dL. For high-frequency only hearing impairment, the prevalence ratio for estimated glomerular filtration rate 30–59 mL/min/1.73 m² was 1.23 (1.03, 1.47) adjusted for age and sex. People with family income less than $20,000 had almost twice the prevalence of hearing impairment (PR = 1.93 (1.34, 2.78)) as people with income over $40,000.

Conclusions

Current smoking, alcohol consumption, high triglycerides, and chronic kidney disease are potentially preventable correlates of hearing impairment for persons with diabetes. Low income is a marker of increased likelihood of hearing impairment.

Relationship between obesity and hearing loss

CONCLUSION

Underweight and severe obesity were associated with an increased prevalence of hearing loss in a Korean population.

OBJECTIVE

The relationship between weight and hearing loss is unclear. This study, therefore, analyzed the relationship between hearing loss and body mass index (BMI) in a Korean population.

METHODS

The prevalence and severity of hearing loss were assessed in 61 052 subjects who underwent health screening examinations, including hearing tests. Subjects were divided into five groups according to BMI (underweight, normal, overweight, obese, and severely obese). The relationships between the prevalence and severity of hearing loss and BMI were analyzed, after adjusting for the effects of age.

RESULTS

The rates of mild or greater hearing loss in the underweight, normal, overweight, obese, and severely obese groups were 24.9%, 20.4%, 21.8%, 21.2%, and 24.1%, respectively. Mild severity of hearing loss was the most common in all five groups, followed by moderate, moderately severe, and severe hearing loss, in that order. Multivariate analysis, showed that the odds ratios of hearing loss in the severely obese, and underweight groups, compared with the normal group, were 1.312 and 1.282, respectively.

Secondhand Smoke is Associated with Hearing Threshold Shifts in Obese Adults

Hearing loss resulted from multiple intrinsic and extrinsic factors. Secondhand smoke (SHS) and obesity had been reported to be related to hearing loss. This study explored the possible associations of SHS and obesity with the hearing threshold. The relations between SHS and the hearing threshold in subjects from three different body mass index classes were analyzed. Our study included data from 1,961 subjects aged 20–69 years that were obtained from the National Health and Nutrition Examination Survey for the years 1999–2004. After adjusting for potential confounding factors, the subjects with the higher tertiles of serum cotinine levels tended to have higher hearing thresholds than those with the lowest tertile of serum cotinine levels (for both trends, p < 0.05). Notably, the obese subjects with the higher tertiles of serum cotinine levels had significantly higher hearing thresholds for high frequencies and low frequencies than those with the lowest tertile of serum cotinine levels (for both trends, p < 0.05). Our study showed a significant positive association between SHS exposure and hearing thresholds in the adult population, especially in obese individuals. Based on our findings, avoiding exposure to SHS, especially in obese adults, may decrease the risk of hearing loss.

Long-term omega-3 fatty acid supplementation prevents expression changes in cochlear homocysteine metabolism and ameliorates progressive hearing loss in C57BL/6J mice

Omega-3 polyunsaturated fatty acids (PUFAs) are essential nutrients well known for their beneficial effects, among others on cognitive development and maintenance, inflammation and oxidative stress. Previous studies have shown an inverse association between high plasma levels of PUFAs and age-related hearing loss, and the relationship between low serum folate and elevated plasma homocysteine levels and hearing loss. Therefore, we used C57BL/6J mice and long-term omega-3 supplementation to evaluate the impact on hearing by analyzing their auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) thresholds. The omega-3 group showed significantly lower ABR hearing thresholds (~25 dB sound pressure level) and higher DPOAE amplitudes in mid-high frequencies when compared to the control group. These changes did not correlate with alterations between groups in plasma homocysteine or serum folate levels as measured by high-performance liquid chromatography and a microbiological method, respectively. Aging in the control group was associated with imbalanced cytokine expression toward increased proinflammatory cytokines as determined by quantitative reverse transcriptase polymerase chain reaction; these changes were prevented by omega-3 supplementation. Genes involved in homocysteine metabolism showed decreased expression during aging of control animals, and only alterations in Bhmt and Cbs were significantly prevented by omega-3 feeding. Western blotting showed that omega-3 supplementation precluded the CBS protein increase detected in 10-month-old controls but also produced an increase in BHMT protein levels. Altogether, the results obtained suggest a long-term protective role of omega-3 supplementation on cochlear metabolism and progression of hearing loss.

Subclinical atherosclerosis and increased risk of hearing impairment

OBJECTIVE

The study's purpose was to test if subclinical atherosclerosis was associated with the risk of developing HI in a large cohort of middle-aged participants.

METHODS

Study subjects were members of the Beaver Dam Offspring Study (BOSS), a longitudinal study of adult children of participants in the population-based Epidemiology of Hearing Loss Study (1993-present). BOSS examinations took place in 2005-2008 (baseline) and 2010-2013 (5-year follow-up). The 5-year incidence of hearing impairment was defined as a pure-tone average (PTA) of thresholds at 0.5, 1, 2 and 4 kHz > 25 dB Hearing Level (dB HL) in either ear at follow-up among participants at risk (baseline PTA in both ears < = 25 dB HL; n = 2436, mean age = 47.7 years). Atherosclerosis was measured as the mean carotid intima-media thickness and the presence of carotid artery plaque.

RESULTS

Among the 1984 participants at-risk with a follow-up audiometric examination, the 5-year incidence of hearing impairment was 8.3% (95% Confidence Interval (C.I.) 7.1, 9.5). With multivariable adjustment, carotid intima-media thickness was positively associated with hearing impairment incidence (Relative Risk (RR) = 1.14 per 0.1 mm, 95% C.I. 1.04, 1.24). The number of sites (0-6) with plaque was also positively associated with the incidence of impairment (RR = 1.16 per site, 95% C.I. 1.01, 1.32).

CONCLUSION

Atherosclerosis was associated with the 5-year incidence of hearing impairment in this predominantly middle-aged cohort. Interventions targeting atherosclerosis prevention may help to prevent or delay the onset of hearing impairment.

Folic acid deficiency induces premature hearing loss through mechanisms involving cochlear oxidative stress and impairment of homocysteine metabolism

Nutritional imbalance is emerging as a causative factor of hearing loss. Epidemiologic studies have linked hearing loss to elevated plasma total homocysteine (tHcy) and folate deficiency, and have shown that folate supplementation lowers tHcy levels potentially ameliorating age-related hearing loss. The purpose of this study was to address the impact of folate deficiency on hearing loss and to examine the underlying mechanisms. For this purpose, 2-mo-old C57BL/6J mice (Animalia Chordata Mus musculus) were randomly divided into 2 groups (n = 65 each) that were fed folate-deficient (FD) or standard diets for 8 wk. HPLC analysis demonstrated a 7-fold decline in serum folate and a 3-fold increase in tHcy levels. FD mice exhibited severe hearing loss measured by auditory brainstem recordings and TUNEL-positive-apoptotic cochlear cells. RT-quantitative PCR and Western blotting showed reduced levels of enzymes catalyzing homocysteine (Hcy) production and recycling, together with a 30% increase in protein homocysteinylation. Redox stress was demonstrated by decreased expression of catalase, glutathione peroxidase 4, and glutathione synthetase genes, increased levels of manganese superoxide dismutase, and NADPH oxidase-complex adaptor cytochrome b-245, α-polypeptide (p22phox) proteins, and elevated concentrations of glutathione species. Altogether, our findings demonstrate, for the first time, that the relationship between hyperhomocysteinemia induced by folate deficiency and premature hearing loss involves impairment of cochlear Hcy metabolism and associated oxidative stress.

Cigarette smoking, passive smoking, alcohol consumption, and hearing loss

The objective of this large population-based cross-sectional study was to evaluate the association between smoking, passive smoking, alcohol consumption, and hearing loss. The study sample was a subset of the UK Biobank Resource, 164,770 adults aged between 40 and 69 years who completed a speech-in-noise hearing test (the Digit Triplet Test). Hearing loss was defined as speech recognition in noise in the better ear poorer than 2 standard deviations below the mean with reference to young normally hearing listeners. In multiple logistic regression controlling for potential confounders, current smokers were more likely to have a hearing loss than non-smokers (odds ratio (OR) 1.15, 95 % confidence interval (CI) 1.09-1.21). Among non-smokers, those who reported passive exposure to tobacco smoke were more likely to have a hearing loss (OR 1.28, 95 %CI 1.21-1.35). For both smoking and passive smoking, there was evidence of a dose-response effect. Those who consume alcohol were less likely to have a hearing loss than lifetime teetotalers. The association was similar across three levels of consumption by volume of alcohol (lightest 25 %, OR 0.61, 95 %CI 0.57-0.65; middle 50 % OR 0.62, 95 %CI 0.58-0.66; heaviest 25 % OR 0.65, 95 %CI 0.61-0.70). The results suggest that lifestyle factors may moderate the risk of hearing loss. Alcohol consumption was associated with a protective effect. Quitting or reducing smoking and avoiding passive exposure to tobacco smoke may also help prevent or moderate age-related hearing loss.

Body mass index, waist circumference, physical activity, and risk of hearing loss in women

BACKGROUND

Acquired hearing loss is highly prevalent, but prospective data on potentially modifiable risk factors are limited. In cross-sectional studies, higher body mass index (BMI), larger waist circumference, and lower physical activity have been associated with poorer hearing, but these have not been examined prospectively.

METHODS

We examined the independent associations between BMI, waist circumference, and physical activity, and self-reported hearing loss in 68,421 women in the Nurses' Health Study II from 1989 to 2009. Baseline and updated information on BMI, waist circumference, and physical activity was obtained from biennial questionnaires.

RESULTS

After more than 1.1 million person-years of follow-up, 11,286 cases of hearing loss were reported to have occurred. Higher BMI and larger waist circumference were associated with increased risk of hearing loss. Compared with women with BMI <25 kg/m(2), the multivariate-adjusted relative risk (RR) for women with BMI ≥ 40 was 1.25 (95% confidence interval [CI], 1.14-1.37). Compared with women with waist circumference <71 cm, the multivariate-adjusted RR for waist circumference >88 cm was 1.27 (95% CI, 1.17-1.38). Higher physical activity was related inversely to risk; compared with women in the lowest quintile of physical activity, the multivariate-adjusted RR for women in the highest quintile was 0.83 (95% CI, 0.78-0.88). Walking 2 hours per week or more was associated inversely with risk. Simultaneous adjustment for BMI, waist circumference, and physical activity slightly attenuated the associations but they remained statistically significant.

CONCLUSIONS

Higher BMI and larger waist circumference are associated with increased risk, and higher physical activity is associated with reduced risk of hearing loss in women. These findings provide evidence that maintaining healthy weight and staying physically active, potentially modifiable lifestyle factors, may help reduce the risk of hearing loss.

White matter hyperintensities predict low frequency hearing in older adults

Vascular disease has been proposed as a contributing factor for presbyacusis (age-related hearing loss). While this hypothesis is supported by pathological evidence of vascular decline in post-mortem human and animal studies, evidence in human subjects has been mixed with associations typically reported between a measure of vascular health and low frequency hearing in older women. Given the difficulty of characterizing the in vivo health of the cochlear artery in humans, an estimate of cerebral small vessel disease was used to test the prediction that age-related change in low frequency hearing and not high frequency hearing is related to a global decline in vascular health. We examined the extent to which these associations were specific to women and influenced by a history of high blood pressure in 72 older adults (mean age 67.12 years, SD = 8.79). Probability estimates of periventricular white matter hyperintensities (WMH) from T1- and fluid attenuated T2-weighted magnetic resonance images were significantly associated with a low frequency hearing metric across the sample, which were independent of age, but driven by women and people with a history of high blood pressure. These results support the premise that vascular declines are one mechanism underlying age-related changes in low frequency hearing.

Association Between Cardiorespiratory Fitness and Hearing Sensitivity

Purpose

As a follow-up to previous smaller scale studies, the purpose of the present study was to examine the link between cardiorespiratory fitness and hearing sensitivity using a nationally representative U.S. sample of adults.

Method

Data from the 1999–2004 National Health and Nutrition Examination Survey (NHANES; U.S. Centers for Disease Control and Prevention [CDC], 2011) were used in the analyses. After exclusions, the final sample included 1,082 NHANES participants ages 20–49 years. Maximum oxygen uptake (VO 2max ) was obtained from an established nonexercise prediction equation and through heart-rate extrapolation during a treadmill-based submaximal test. Audiometry data were objectively measured to obtain estimates of low (LPTA) and high (HPTA) pure-tone frequency average.

Results

VO 2max was not associated with hearing sensitivity when using the heart-rate extrapolation method but was significantly associated with hearing sensitivity (for women) when applying the nonexercise prediction equation for both LPTA and HPTA ( p < .01). Women with higher predicted cardiorespiratory fitness were 6% more likely than women with lower predicted cardio-respiratory fitness to have good hearing compared to worse hearing.

Conclusion

Cardiorespiratory fitness was associated with hearing sensitivity when using the nonexercise prediction equation to measure VO 2max . Further studies are needed to confirm these findings. Findings suggest a potentially auditory-protective effect of cardiorespiratory fitness.

The influence of cardiovascular health on peripheral and central auditory function in adults: a research review

PURPOSE

This article provides a comparative review of research that has been conducted over the past 60+ years on the influence of cardiovascular health on the function of the peripheral and central auditory systems, and findings on the influence of improvements in cardiovascular health on those same systems.

METHOD

Research spanning the past 6 decades reviewed for this article has both hypothesized and confirmed the cardiovascular system's effects on the peripheral and central auditory systems. A review of the influence of the cardiovascular system is presented in this article, and a potential new avenue for auditory rehabilitation is postulated. The review presented in this article does not represent all studies conducted in the topic area but does provide an in-depth look into this fascinating area of research.

CONCLUSIONS

The negative influence of impaired cardiovascular health on both the peripheral and central auditory system and the potential positive influence of improved cardiovascular health on these same systems have been found through a sizable body of research that has been conducted over more than 6 decades. The most significant positive relationship between improved cardiovascular health and improvements in those auditory systems has been found among older adults. If that relationship continues to be confirmed, then a potential new avenue for auditory rehabilitation on behalf of adults who possess impaired auditory function may be discovered.

Potential mediators of diabetes-related hearing impairment in the U.S. population: National Health and Nutrition Examination Survey 1999-2004

OBJECTIVE

We examined potential mediators of the reported association between diabetes and hearing impairment.

RESEARCH DESIGN AND METHODS

Data come from 1,508 participants, aged 40-69 years, who completed audiometric testing during 1999-2004 in the National Health and Nutrition Examination Survey (NHANES). We defined hearing impairment as the pure-tone average >25 decibels hearing level of pure-tone thresholds at low/mid (500, 1,000, and 2,000 Hz) and high (3,000, 4,000, 6,000, and 8,000 Hz) frequencies. Using logistic regression, we examined whether controlling for vascular or neuropathic conditions, cardiovascular risk factors, glycemia, or inflammation diminished the association between diabetes and hearing impairment.

RESULTS

Diabetes was associated with a 100% increased odds of low/mid-frequency hearing impairment (odds ratio 2.03 [95% CI 1.32-3.10]) and a 67% increased odds of high-frequency hearing impairment (1.67 [1.14-2.44]) in preliminary models after controlling for age, sex, race/ethnicity, education, smoking, and occupational noise exposure. Adjusting for peripheral neuropathy attenuated the association with low/mid-frequency hearing impairment (1.70 [1.02-2.82]). Adjusting for albuminuria and C-reactive protein attenuated the association with high-frequency hearing impairment (1.54 [1.02-2.32] and 1.50 [1.01-2.23], respectively). Diabetes was not associated with high-frequency hearing impairment after controlling for A1C (1.09 [0.60-1.99]) but remained associated with low/mid-frequency impairment. We found no evidence suggesting that our observed relationship between diabetes and hearing impairment is due to hypertension or dyslipidemia.

CONCLUSIONS

Mechanisms related to neuropathic or microvascular factors, inflammation, or hyperglycemia may be mediating the association of diabetes and hearing impairment.

Hypertensive retinopathy and sensorineural hearing loss

OBJECTIVE

To determine the correlation between hypertensive retinopathy (which is the end-organ damage of the vessels due to chronic hypertension) with sensorineural hearing loss.

METHODS

Pure tone hearing threshold of 56 hypertensive patients were compared with 56 normal age and sex matched control. Comparisons of pure tone hearing threshold are made among different group (grade) of hypertensive retinopathy patients and control (non-hypertensive patients).

RESULTS

The mean hearing thresholds were higher (worse) in all the frequencies on both sides in the hypertensive study group compared with normal subjects. However it was found to be statistically significant when tested using independent sample test (p < 0.05) on right ear at 2,000 Hz, 4,000 Hz and 8,000 Hz only. The mean hearing threshold is higher in all frequencies in the presence of retinopathy compared to control. However, the difference was found to be only statistically significant in the mean hearing threshold between grade I and control at 4,000 Hz and 8,000 Hz on both sides and at 1,000 Hz and 2,000 Hz on right ear. Hypertensive patient with grade I retinopathy had higher pure tone hearing thresholds at 4,000 Hz and 8,000 Hz compared to hypertensive without retinopathy and normal control.

CONCLUSIONS

Hypertensive retinopathy appears to be associated with high frequency sensor neural hearing loss.

Associations of carotid intima-media thickness, tobacco smoking and overweight with hearing disorder in a general population sample

It has been argued that smoking or overweight might contribute to hearing disorder by atherogenic narrowing of the nutrient arteries to the cochlea. The carotid intima-media thickness (CIMT) is a surrogate marker for generalized atherosclerosis. We analyzed a subgroup (n=2619) from a general population sample in north-eastern Germany aged 45-81 years (Study of Health in Pomerania, SHIP). Assessments included self-statements about hearing disorder and medical examinations of CIMT. Using ordinal logistic regression for data analysis and after adjustment for cigarettes per day, waist circumference, diabetes, exposure to noise, age and sex, we found CIMT remained a predictor of hearing disorder (odds ratio 1.8, 95% confidence interval 1.0-3.2). Cigarettes per day and waist circumference were related to CIMT but not to hearing disorder. The findings suggest a positive association between CIMT and hearing disorder.

Association of folate with hearing is dependent on the 5,10-methylenetetrahdyrofolate reductase 677C-->T mutation

Vascular disease and its risk factors have been associated with the age-related hearing loss. We examined the association of elevated plasma homocysteine and its determinants with hearing levels. Pure-tone air conduction thresholds in 728 individuals with sensorineural hearing loss were not associated with homocysteine, erythrocyte folate and Vitamin B6. Low concentrations of serum folate and Vitamin B12 were associated with better hearing. When folate status was below the median, 5,10-methylenetetrahydrofolate reductase (MTHFR) 677TT homozygotes had similar hearing levels to subjects with a C allele. However, when folate status was above the median, MTHFR 677TT homozygotes had on an average 5 dB (p = 0.037) and 2.6 dB (p = 0.021) lower PTA-high and PTA-low hearing thresholds, respectively, than the subjects with a 677C allele. The relationship between serum folate and hearing thresholds appeared to be dependent on MTHFR 677 genotype (CC, r = 0.13, p = 0.034; TT, r = -0.10, p = 0.291). This supports the hypothesis that a greater one-carbon moiety commitment to de novo synthesis of nucleotides and an increase in formyl-folate derivatives relative to methyl-folate derivatives is protective for hearing.

The association between cardiovascular disease and cochlear function in older adults

The purpose of this research was to evaluate the relation between self-reported cardiovascular disease (CVD) and cochlear function in older adults. The Epidemiology of Hearing Loss Study (EHLS) is an ongoing population-based study of hearing loss and its risk factors in Beaver Dam, Wisconsin. As part of the EHLS questionnaire, participants were asked about their cardiovascular medical history. CVD history was determined from questions regarding history of angina, myocardial infarction (MI), and stroke. Questions about the use of antihypertensive medication and blood pressure measurements determined the presence or absence of hypertension. Among the audiologic measures completed were distortion product otoacoustic emissions (DPOAEs). Cochlear function was measured using DPOAEs and participants were categorized as having (a) cochlear impairment, (b) possible cochlear impairment, or (c) no cochlear impairment. There were 1,501 participants with complete CVD and DPOAE data from the 1998-2000 examination phase. Women with a self-reported history of MI were twice as likely (age-adjusted odds ratio [OR] = 2.00, 95% confidence interval [CI] = 1.15-3.46) to have cochlear impairment than women without a history of MI. This association was not significant in men (age-adjusted OR = 0.98, 95% CI = 0.61-1.58). Additionally, no other CVD variables were associated with cochlear impairment. This study provides data on a possible sex-specific association between CVD and DPOAEs in older adults.

Hearing loss associated with smoking and occupational noise exposure in a Japanese metal working company

The effects of smoking on hearing loss within the context of atherosclerosis was assessed, and the statistical interaction of occupational noise evaluated. A cross-sectional study was conducted in 397 Japanese males working at a metal factory, aged 21-66 years, in a periodical health checkup. The following information was obtained: two smoking indices of smoking status and Brinkman index, occupational noise exposures and atherosclerotic risk factors (body mass index, blood pressure, serum cholesterol, hemoglobin A1c, atherosclerosis index). Hearing acuity was measured at 4 kHz using a pure-tone audiometer in a quiet room. Among the total subjects, 55 (13.9%) were identified as having hearing loss at 4 kHz, and 151 (38.0%) were currently exposed to occupational noise. When adjusted for age and occupational noise exposure, odds ratios (95% confidence intervals) of hearing loss were 3.16 (1.04, 9.62) for past smokers and 3.39 (1.05, 11.01) for heavy smokers (Brinkman index >750 cigarettes per day x number of years), compared with never-smokers. Statistical interaction of occupational noise exposure was insignificant with the association between smoking and hearing loss. When including atherosclerotic risk factors in a multiple model, there were no significant associations between hearing loss and either smoking or any other factors (i.e., occupational noise and atherosclerotic factors). Smoking was found to be associated with hearing loss beyond occupational noise exposure, and this association seemed to be masked by atherosclerotic factors, suggesting that the direction of the atherosclerotic effect on the relationship might need to be explored between smoking and hearing impairment.

A prospective case-control study of 50 consecutive patients presenting with hyperlipidaemia

The literature contains many references which refer to a causal relationship between hyperlipidaemia and hearing loss, but the majority of reports lack adequate controls, or are based on a series of cases which may represent incidental findings. This prospective case-control study compared a restricted population of 50 consecutive hyperlipidaemic patients attending a lipid clinic whose fasting lipid levels were > 2 SDs above the population mean with a control population recruited from patients undergoing nasal surgery for structural abnormalities (n = 159). The National Study of Hearing data was also compared with both groups in order to provide external validity to the control group. This study showed no consistent differences in the hearing thresholds of the hyperlipidaemic group compared with either control group. The Null hypothesis that sensorineural hearing loss is no greater in a population whose fasting blood lipids are raised > 2 SDs above the population mean level than in a control population cannot be refuted given the variability of the data.

Moderate alcohol consumption and hearing loss: a protective effect

OBJECTIVE

To determine if moderate alcohol consumption is associated inversely with hearing loss in a large population based study of older adults.

DESIGN

Cross-sectional population based cohort study. Data are from the 1993-1995 examinations for the population based Epidemiology of Hearing Loss Study (EHLS) (n = 3571) and the Beaver Dam Eye Study (BDES) (n = 3722).

SETTING

Midwestern community of Beaver Dam, Wisconsin.

PARTICIPANTS

Residents of Beaver Dam aged 43 to 84 in 1987-1988 were eligible for the BDES (examinations in 1988-1990 and 1993-1995). During 1993-1995, this same cohort was eligible to participate in the baseline examination for the EHLS.

MEASUREMENTS

Hearing thresholds were measured by pure tone air and bone conduction audiometry (250-8000 Hz.). History of alcohol consumption in the past year, heavy drinking (ever), medical history, occupation, noise exposure, and other lifestyle factors were ascertained by a questionnaire that was administered as an interview.

RESULTS

In multiple logistic regression analyses controlling for potential confounders, moderate alcohol consumption (>140 grams/week) was inversely associated with hearing loss (PTA(.5,1,2,4 > 25 dB HL); odds ratio [OR] = .71, 95% confidence interval [CI] = .52, .97; where PTA is pure tone average). A similar association was found for moderate hearing loss (PTA(.5,1,2,4 > 40 dB HL); OR = 0.49, 95% CI = 0.32, 0.74). Alcohol consumption was associated inversely with the odds of having a low frequency hearing loss (OR = 0.61) or a high frequency hearing loss (OR = 0.60). These findings did not vary significantly by age or gender. There was an increase in the odds of having a high frequency hearing loss (OR = 1.35, 95% CI = 1.04, 1.75), in those with a history of heavy drinking (> or =4 drinks/day). Including cardiovascular disease or its related factors did not significantly attenuate the protective effect.

CONCLUSIONS

There is evidence of a modest protective association of alcohol consumption and hearing loss in these cross-sectional data. This finding is in agreement with a small body of evidence suggesting that hearing loss is not an inevitable component of the aging process.

Smoking as a risk factor in sensory neural hearing loss among workers exposed to occupational noise

The effect of smoking on hearing was investigated among 199 professional forest workers and 171 shipyard workers. The effect of age on hearing was corrected with Robinson's model for an audiologically screened population. The exposure of the subjects to noise and their history of tobacco smoking were examined, with special reference to blood pressure and occupational Raynaud's phenomenon. Smoking without the presence of any other risk factors did not increase the risk for sensory neural hearing loss, but smoking in combination with elevated blood pressure and occupational Raynaud's phenomenon put workers at higher risk for hearing loss than any of these factors alone.

Interaction between hypertension and diabetes mellitus in the pathogenesis of sensorineural hearing loss

The purpose of this study is to support the hypothesis that diabetic end-organ damage of the cochlea is augmented in the setting of hypertension. A historical perspective reviewing the effects of diabetes and hypertension as causative factors in the development of sensorineural hearing loss, as well as the basic epidemiology and pathophysiology of the renal and vascular effects of diabetes and hypertension, is presented. The results of audiologic findings in insulin-dependent diabetic patients, both normotensive and hypertensive, were analyzed and correlated with the results of animal studies to support the hypothesis that sensorineural hearing loss in patients and cochlear hair cell loss in animal studies result from the effects of hypertension in conjunction with insulin-dependent diabetes mellitus.

Clinical investigation of hearing loss in the elderly

The prevalence of hearing loss increases with age. Epidemiological and histopathological studies relating hearing loss to age are reviewed and clinical evidence presented suggesting that hearing loss is due not only to age but also to disease processes known to be associated with hearing threshold deterioration. 80 elderly patients presenting with a hearing problem at hospital have been studied and compared with 287 'non-complainers'. 83% of the study group were found to have factors, additional to age, contributing to their hearing loss; 50% had a medical condition previously unrecognized; 30% were taking potentially ototoxic drugs. Audiometric measurements indicate that hearing thresholds of the elderly are influenced by numerous disease processes. Patients attending hospital with hearing impairment are at greater risk of having a vascular or biochemical abnormality than a group of elderly 'non-complainers'. Elderly patients presenting with hearing loss should therefore be adequately investigated before being labelled as having presbyacusis.

Age-related cochlear hair cell loss in the chinchilla

The spiral organ of the chinchilla was studied by the surface-preparation technique in four different age groups: 1 month, 6 months, 1 year, and 4 years, to assess age-related hair cell loss. Decrease in hair cell population is linearly related to age, and damage rate of outer hair cells is greater than that of inner hair cells. The mean percentage of damaged total outer hair cells was 0.60%, 1.16%, 1.71%, and 7.07% in animals in 1 month, 6 months, 1 year, and 4 years of age, respectively. Outer hair cell loss was greatest in the apex of the cochlea and, of these cells, the outermost row was the most affected. Damage to inner hair cells also increases with age. Age-related apical cochlear cell loss in the chinchilla is comparable to that observed in other laboratory animals.

Auditory brainstem responses (ABR) in the aged

86 male subjects, aged between 60 and 86 years (M = 69.5), underwent pure-tone audiometry, impedance tests and brainstem response audiometry (BRA). Subjects have been classified into four age-related groups: 1) 34 subjects, aged between 60 and 65; 2) 22, aged between 66 and 70; 3) 22 aged between 71 and 75; 4) 8, aged between 76 and 86. They have also been classified into four groups on the basis of their mean auditory threshold at 0.5, 1, 2, 4 and 8 kHz: 1) 14 subjects with mean auditory threshold less than or equal to 30 dB HL; 2) 16, between 31 and 40; 3) 24, between 41 and 50; 4) 32, with mean auditory threshold greater than or equal to 51 dB HL. 19 normally hearing adults, aged between 28 and 42, were chosen as controls. Statistically significant correlations have been found between age and mean auditory threshold (P less than or equal to 0.001), between wave latency V and age (P less than or equal to 0.001), between wave latency V and the mean pure-tone auditory threshold at 0.5, 1, 2, 4 and 8 kHz (P less than or equal to 0.001) and between the V-I interval and age (P less than or equal to 0.001). The discrepancy between the mean auditory threshold and the ABR waveform, the overall amplitude's reduction of ABR waves and the progressive lengthening of V-I interval values, seem to indicate that age-related changes involve not only the end organ but also the brainstem auditory structures.