Effects of acute and chronic hypertension on the labyrinthine barriers in rat

Hearing Loss and Hypertension: A Literature Review

Hypertension is a condition in which there is an abnormal blood pressure with a systolic pressure of more than 140 mmHg and a diastolic pressure of more than 90 mmHg. It has been cited that hypertension can cause hearing loss. To understand the association between hypertension and hearing loss, a systematic review has been carried out in Pubmed Central, Google Scholar, EBSCO, Web of Science, Indian Science Abstracts, J Gate, Proquest, and Shodh Ganga. This review included original articles published on or after 2016 with cross-sectional study design, retrospective study design, and longitudinal design and excluded case reports and letters to the editors. Out of the 11,977 articles, only ten articles were finalized. These 10 articles stated a possible association between hypertension and hearing loss by explaining that Cochlear microcirculation change resulted in tissue hypoxia that caused hearing loss.

Association Between Nonoptimal Blood Pressure and Cochlear Function

OBJECTIVES

The association between hearing loss and risk factors for cardiovascular disease, including high blood pressure (BP), has been evaluated in numerous studies. However, data from population- and laboratory-based studies remain inconclusive. Furthermore, most prior work has focused on the effects of BP level on behavioral hearing sensitivity. In this study, we investigated cochlear integrity using distortion product otoacoustic emissions (DPOAEs) in persons with subtle elevation in BP levels (nonoptimal BP) hypothesizing that nonoptimal BP would be associated with poorer cochlear function.

DESIGN

Sixty individuals [55% male, mean age = 31.82 (SD = 11.17) years] took part in the study. The authors measured pure-tone audiometric thresholds from 0.25 to 16 kHz and computed four pure-tone averages (PTAs) for the following frequency combinations (in kHz): PTA0.25, 0.5, 0.75, PTA1, 1.5, 2, 3, PTA4, 6, 8, and PTA10, 12.5, 16. DPOAEs at the frequency 2f1-f2 were recorded for L1/L2 = 65/55 dB SPL using an f2/f1 ratio of 1.22. BP was measured, and subjects were categorized as having either optimal BP (systolic/diastolic <120 and <80 mm Hg) or nonoptimal BP (systolic ≥120 or diastolic ≥80 mm Hg or use of antihypertensives). Between-group differences in behavioral thresholds and DPOAE levels were evaluated using 95% confidence intervals. Pearson product-moment correlations were run to assess the relationships between: (1) thresholds (all four PTAs) and BP level and (2) DPOAE [at low (f2 ≤ 2 kHz), mid (f2 > 2 kHz and ≤10 kHz), and high (f2 > 10 kHz) frequency bins] and BP level. Linear mixed-effects models were constructed to account for the effects of BP status, stimulus frequency, age and sex on thresholds, and DPOAE amplitudes.

RESULTS

Significant positive correlations between diastolic BP and all four PTAs and systolic BP and PTA0.25, 0.5, 0.75 and PTA4, 6, 8 were observed. There was not a significant effect of BP status on hearing thresholds from 0.5 to 16 kHz after adjustment for age, sex, and frequency. Correlations between diastolic and systolic BP and DPOAE levels were statistically significant at the high frequencies and for the relationship between diastolic BP and DPOAE level at the mid frequencies. Averaged across frequency, the nonoptimal BP group had DPOAE levels 1.50 dB lower (poorer) than the optimal BP group and differences were statistically significant (p = 0.03).

CONCLUSIONS

Initial findings suggest significant correlations between diastolic BP and behavioral thresholds and diastolic BP and mid-frequency DPOAE levels. However, adjusted models indicate other factors are more important drivers of impaired auditory function. Contrary to our hypothesis, we found that subtle BP elevation was not associated with poorer hearing sensitivity or cochlear dysfunction. We consider explanations for the null results. Greater elevation in BP (i.e., hypertension itself) may be associated with more pronounced effects on cochlear function, warranting further investigation. This study suggests that OAEs may be a viable tool to characterize the relationship between cardiometabolic risk factors (and in particular, stage 2 hypertension) and hearing health.

Neurobiology of Stress-Induced Tinnitus

Emotional stress has accompanied humans since the dawn of time and has played an essential role not only in positive selection and adaptation to an ever-changing environment, but also in the acceleration or even initiation of many illnesses. The three main somatic mechanisms induced by stress are the hypothalamus-pituitary-adrenal axis (HPA axis), the sympathetic-adreno-medullar (SAM) axis, and the immune axis. In this chapter, the stress-induced mechanisms that can affect cochlear physiology are presented and discussed in the context of tinnitus generation and auditory neurobiology. It is concluded that all of the presented mechanisms need to be further investigated. It is advised that clinical practitioners ask patients about stressful events or chronic stress preceding the tinnitus onset and measure the vital signs. Finally, taking into account that tinnitus itself acts as a stressor, the implementation of anti-stress therapies for tinnitus treatment is recommended.

Relationship of Overall Cardiovascular Health and Hearing Loss in The Jackson Heart Study Population

OBJECTIVES

To evaluate the relationships among the overall cardiovascular health scoring tool, Life's Simple 7 (LS7), and hearing in an African-American cardiovascular study cohort.

METHODS

Using the Jackson Heart Study's cohort of African Americans, the relationships between the LS7 scoring metric and hearing of 1314 individuals were assessed. Standard audiometric data was collected and hearing loss was defined as a four-frequency average of 500, 1000, 2000, and 4000 Hz greater than 25 dBHL (PTA4). Measures of reported tinnitus and dizziness were also collected. The LS7 scoring tool, which consists of seven individual categories (abstinence from smoking, body mass index, physical activity, healthy diet, total cholesterol <200 mg/dL, normotension, and absence of diabetes mellitus), was used as measure of overall cardiovascular health. Each category of the LS7 was broken down into poor, intermediate, and ideal subgroups as in accordance with the American Heart Association Strategic Planning Task Force and Statistics Committee. Unadjusted and adjusted gamma regression and logistic regression models were constructed for determining relationships between LS7 and hearing loss.

RESULTS

Higher total LS7 scores (per 1-unit increase) were associated with lower PTA4 in gamma regression analyses (RR = 0.942, 95% CI, 0.926-0.958, P < .001). This held true even after adjustments for age, sex, education, and history of noise exposure. Using logistic regression analyses to compare LS7 scores to presence of hearing loss, tinnitus, and vertigo; only hearing loss showed a statically significant relationship after adjustments for age, sex, education, and history of noise exposure.

CONCLUSIONS

This study shows a significant, graded association between higher life's simple seven scores and lower incidence of hearing loss.

LEVEL OF EVIDENCE

2b. Laryngoscope, 2019.

Hypertension is associated with dysfunction of both peripheral and central auditory system

OBJECTIVES

Arterial hypertension negatively influences the peripheral auditory system, causing sensorineural hearing loss. Much less is known about the detrimental effects of hypertension on the central auditory functions.

METHODS

We tested 32 arterial hypertension patients and 32 age and sex-matched healthy volunteers with the expanded tonal audiometry (0.125-12.5 kHz), distortion product otoacoustic emissions (0.75-8 kHz), horizontal minimum audible angle test for eight azimuths with binaural stimulation and the random gap detection test.

RESULTS

Peripheral hearing of the hypertensive patients was impaired in comparison with the controls within all audiometric frequencies (0.125-12.5 kHz) and within specific groups of frequencies. Distortion product otoacoustic emission results were significantly lower for frequencies 4 (P = 0.04) and 6 kHz (P < 0.001). The sound localization ability in the horizontal minimum audible angle test was significantly worse in the hypertensive patients in the 0°, 45°, 90°, 135°, and 270° azimuth when the interaural pure tone average (0.5-1-2 kHz) was set less than 20 dB hearing level (P < 0.05), and in the 0°, 90°, 225°, and 270°azimuth when the binaural pure tone average (0.5-1-2 kHz) was set 20 dB or less hearing level (P < 0.05). Gap detection thresholds in the random gap detection test did not differ between the two groups.

CONCLUSION

Arterial hypertension is independently related to the damage of the peripheral part of the auditory system resulting in high-frequency hearing loss. Hypertensive disturbances of central auditory processing are more discrete and concern the spatial hearing resolution.

Positive Association between Tinnitus and Arterial Hypertension

INTRODUCTION

Tinnitus is the perception of noise in the absence of an external source and is considered by most authors as a multifactorial symptom. A systematic review concerning the association of tinnitus and systemic arterial hypertension retrieved suggestions of a positive association, but the articles included failed to perform a detailed analysis on the theme.

PURPOSE

To analyze the presence of arterial hypertension in tinnitus and non-tinnitus patients, to analyze differences between tinnitus impact and psychoacoustic measurements in hypertensive and normotensive patients, and to evaluate the association between the presence of tinnitus and the diverse antihypertensive drugs employed.

MATERIALS AND METHODS

This includes cross-sectional transversal study, comparing two groups of subjects (144 in the study group with tinnitus and 140 in the control group without tinnitus). Clinical, demographical, audiometrical, and psychoacoustics characteristics of the subjects were compared.

RESULTS

Hypertension prevalence in tinnitus subjects was 44.4% against 31.4% in subjects without tinnitus (p = 0.024). Positive associations with tinnitus were found with hypertension treatment with angiotensin-converting enzyme (ACE) inhibitors (p = 0.006), tiazidic diuretics (p < 0.0001), potassium-sparing diuretics (p = 0.016), and calcium channels blockers (p = 0.004).

CONCLUSION

There is an association between tinnitus and arterial hypertension. This association is particularly strong in older patients. Hypertension treatment with diuretics, ACE inhibitors, and calcium channels blockers were more prevalent in tinnitus patients, suggesting that an eventual ototoxicity of these drugs may be involved in tinnitus pathophysiology, a hypothesis that should be evaluated in further studies.

Interaction between diabetes mellitus and hypertension on hearing of elderly

INTRODUCTION

Chronic diseases and metabolic changes may act as accelerating factor in the degeneration of the auditory system due to age. However, studies involving an association between hearing loss and diabetes mellitus (DM) and hypertension (HA) in the elderly have shown controversial conclusions. Thus, further studies on this topic are needed in order to elucidate the effect of these chronic diseases on the auditory system.

AIM

To compare the hearing thresholds of elderly patients with DM, HA and DM + HA with a control group (CG).

METHODS

Retrospective study was conducted through survey charts of 80 elderly people with full hearing assessment, between 2008 and 2012. Subjects were divided into four groups: DM, HA, DM + HA and without chronic diseases known (CG). The ANOVA, Tukey and Mauchly tests, with a significance level of 0.05, were used.

RESULTS

There was no statistically significant difference between the ears, which are grouped. Comparisons between the means of hearing thresholds of CG and DM or HA showed no statistically significant differences. However, a statistically significant difference in the comparison between these three groups and DM + HA group for several of the frequencies evaluated was observed.

CONCLUSION

It was found that older adults with DM and hypertension associated showed greater hearing impairment in comparison with the other groups, suggesting a synergistic effect of the two chronic diseases on hearing.

The audiological profile of adults with and without hypertension

OBJECTIVE

To determine whether there is any influence of systemic arterial hypertension on the peripheral auditory system.

METHODS

This was a cross-sectional study that investigated 40 individuals between 30 and 50 years old, who were divided into groups with and without systemic arterial hypertension, using data from high-frequency audiometry, transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions. The results were compared with those from groups of normal-hearing individuals, with and without systemic arterial hypertension, who underwent the pure-tone audiometry test. All individuals also underwent the following procedures: otoscopy, acoustic immittance measures, pure-tone audiometry at frequencies from 250 to 16000 Hz, transient-evoked otoacoustic emissions test and distortion-product otoacoustic emissions test.

RESULTS

No statistically significant difference was observed between the groups with and without systemic arterial hypertension in either conventional or high-frequency audiometry. Regarding transient-evoked otoacoustic emissions, there was a trend toward statistical significance whereby the systemic arterial hypertension group showed lower results. Regarding distortion-product otoacoustic emissions, the systemic arterial hypertension group showed significantly lower results at the following frequencies: 1501, 2002, and 3003 Hz. A discriminant analysis indicated that the distortion-product otoacoustic emissions variables best distinguished individuals with and without systemic arterial hypertension.

CONCLUSION

Data from this study suggest cochlear dysfunction in individuals with systemic arterial hypertension because their otoacoustic emission results were lower than those in the systemic arterial hypertension group.

Comment on "Mutual suppression in the 6 kHz region of sensitive chinchilla cochleae" [J. Acoust. Soc. Am. 121, 2805-2818 (2007)]

Rhode [J. Acoust. Soc. Am. 121, 2805-2818 (2007)] acknowledges that two-tone neural rate responses for low-side suppression differ from those measured in basilar membrane mechanics, making one question whether this aspect of suppression has a mechanical correlate. It is suggested here that signal coding between mechanical and neural processing stages may be responsible for the fact that the total rate response (but not the basilar membrane response) for low-frequency suppressors is smaller than that for the probe-alone condition. For example, the velocity dependence of inner hair cell (IHC) transduction, membrane/synaptic filtering and the sensitivity difference between ac and dc components of the IHC receptor potential all serve to reduce excitability for low-side suppressors at the single-unit level. Hence, basilar membrane mechanics may well be the source of low-side suppression measured in the auditory nerve.

Systemic high blood pressure and inner ear dysfunction: a preliminary study

OBJECTIVE

To assess the association between inner ear dysfunction and retinal vascular changes related to systemic arterial hypertension.

DESIGN

A comparative, cross-sectional and observational study.

SETTING

Primary care.

MAIN OUTCOMES MEASURES

Hearing and vestibular symptoms evaluated by a standardized questionnaire; cochlear function evaluated by audiometry and distortion product otoacoustic emissions; vestibular function evaluated by oculomotor and bithermal caloric tests and vascular retinal compromise evaluated by ophthalmoscopy (according to the modified Scheie classification).

RESULTS

Forty-two subjects participated in the study, 21 with and 21 without arterial hypertension, age and sex matched; with no history of diabetes mellitus and with normal glucose levels and normal blood lipids. Although patients with hypertension reported vertigo more frequently than control subjects, conventional oculomotor and bithermal caloric tests showed no difference between the two groups. Patients with hypertension showed deterioration of hearing thresholds at 8 kHz and, compared with normotensive subjects, a higher frequency of abnormal otoacoustic emissions (P = 0.01). According to Scheie classification, 43% (95% CI: 33-53%) of the patients showed second degree retinal vascular compromise and 24% (95% CI: 15-33%) of them showed first degree compromise. The degree of the vascular retinal compromise was significantly correlated with the hearing thresholds at 8 kHz (Spearman's correlation coefficient 0.45, P = 0.002) and it was also consistent with the absence of otoacoustic emissions at frequencies between 4 and 8 kHz.

CONCLUSION

The results of this preliminary study suggest that patients with systemic arterial hypertension may have cochlear dysfunction associated with the vascular disease because of hypertension, which could be silent and without clear evidence of vestibular dysfunction.

Mutual suppression in the 6 kHz region of sensitive chinchilla cochleae

Basilar membrane (BM) vibration was measured using a displacement measuring interferometer for single-tone and two-tone suppression (2TS) paradigms in the 6-9 kHz region of sensitive chinchilla cochleae that had gains near or better than 60 dB. Based on prior studies of basilar membrane vibration, three significant differences remain between BM and auditory nerve (AN) 2TS responses: (1) suppression thresholds in the tail of tuning curves were much higher in BM than the auditory nerve (AN); (2) rates of suppression were significantly higher in AN than BM; and (3) the amplitude of vibration with low-frequency suppressors was always greater than the single-tone displacement rendering it impossible to explain 2TS rate suppression in the AN. The first two differences are eliminated by the results of the present study while the third remains. Suppression amplitudes greater than 40 dB and rates of suppression larger than 2.5 dB/dB were found for low-frequency suppressors. A correlation between both the gain and nonlinearity of the cochlea and 2TS properties indicates that when sensitive cochleae are studied. The third difference between BM and AN behavior could be strictly a function of the high-pass filter characteristic of the inner hair cells.

Efficacy of misoprostol in the treatment of tinnitus in patients with diabetes and/or hypertension

OBJECTIVE

To determine the efficacy of the prostaglandin E1 analogue misoprostol in the treatment of tinnitus in diabetic and/or hypertensive patients.

DESIGN

Double-blind, randomized, placebo-controlled trial.

SETTINGS

Tertiary care referral center.

METHODS

The subjects were 42 patients with hypertension and/or diabetes mellitus who had chronic tinnitus and had experienced tinnitus symptoms for a minimum of 6 months. Twenty-eight patients were randomly assigned to Group I (misoprostol treatment), and 14 patients to the Group II (placebo treatment). Misoprostol therapy was started at 200 microg per day, and was increased 200 microg every 7 days until a dose of 800 microg per day was reached. The same numbers of placebo tablets were given to the control group using the same schedule. Both groups were treated for 1 month. The changes in objective and subjective tinnitus findings from baseline to 1 month were assessed, and the group results were compared. The chi(2)-test, student's t-test and paired-samples t-test were used to analyze the study.

RESULTS

At the completion of treatment, objective assessment showed that tinnitus loudness decreased in 13 (46%) of the 28 patients in the experimental group, whereas this was observed in only two (14%) of the 14 subjects in the placebo group. Subjective tinnitus scoring revealed improvement rates of 29 and 14% for the misoprostol and placebo groups, respectively. When t-test relating to difference between rates were performed, the difference between improvement rate for tinnitus loudness of the experimental group and control group was found to be statistically significant (P = 0.05), but difference between improvement rate based on subjective tinnitus scoring was insignificant (P = 0.22).

CONCLUSION

Misoprostol is an effective and safe treatment for chronic tinnitus in hypertensive and/or diabetic patients. Our results are encouraging, but further studies of larger series are needed.