[Audiometric threshold studies on progression & characteristics of presbycusis in various stages of life; with a contribution to the pathogenesis of presbycusis].
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Audiometry↗
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Presbycusis in Nigerians at the University College Hospital, Ibadan.
Presbycusis refers to sensori-neural hearing impairment in elderly individuals resulting from the degenerative changes of aging. Characteristically, it involves bilateral sensorineural hearing loss, worse at high frequencies, which is associated with difficulty in speech discrimination and central auditory processing of information. The aim of this study is to present our observations on presbycusis as seen in Nigerians. A 41/2-year prospective study of 67 patients that presented with features of presbycusis in the Ear, Nose and Throat Department of the University College Hospital, Ibadan, Nigeria between January 2000 and June 2004 was done. The diagnosis of presbycusis in each subject was based on history, clinical findings, and pure tone audiometry. 67 patients with features of presbycusis were seen and treated over the studied period with 37 males (55.2%), 30 females (44.8%) (M:F 1.2:1) and with an average age of 69.3 years (age range 46-90 years). Presbycusis constituted 2.4% of the 2817 otological cases seen during the studied period. Majority (64.1%) of the cases were of 6th to 8th decades of life. The symptoms were mainly of hearing loss 34 (50.7%), tinnitus 19 (28.4%), hearing loss and tinnitus together in 14 (20.9%) cases. Stria (metabolic) presbycusis 20 (29.9%) constituted the most common type of presbycusis seen in this study followed by mechanical presbycusis 15 (22.4%), neural presbycusis 14 (20.9%) and sensory presbycusis 7 (10.4%) respectively. Presbycusis has been found in this study to affect both males and females subjects almost equally, has an insidious onset as from fourth decades of life in our environment, of stria (metabolic) type mostly, presents with moderate to severe sensori-neural hearing loss (SNHL), and constitute an important problem in the society as it occurs in an elderly population that relies on their special senses (especially auditory) to compensate for other age-associated disabilities.
Age Factors↗
Cochlear pathology in presbycusis.
A survey of the temporal bone collection at the Massachusetts Eye and Ear Infirmary reveals 21 cases that meet the criterion for the clinical diagnosis of presbycusis. It is evident that the previously advanced concept of four predominant pathologic types of presbycusis is valid, these being sensory, neural, strial, and cochlear conductive. An abrupt high-tone loss signals sensory presbycusis, a flat threshold pattern is indicative of strial presbycusis, and loss of word discrimination is characteristic of neural presbycusis. When the increments of threshold loss present a gradually decreasing linear distribution pattern on the audiometric scale and have no pathologic correlate, it is speculated that the hearing loss is caused by alterations in the physical characteristics of the cochlear duct, and the loss is identified as cochlear conductive presbycusis. It is clear that many individual cases do not separate into a specific type but have mixtures of these pathologic types and are termed mixed presbycusis. About 25% of all cases of presbycusis show none of the above characteristics and are classified as indeterminate presbycusis.
Aged↗
N-acetyltransferase 2 gene polymorphism and presbycusis.
OBJECTIVES/HYPOTHESIS: The enzyme of N-acetyltransferase (NAT) is involved in the metabolism and detoxification of cytotoxic and carcinogenic compounds as well as reactive oxygen species (ROS). The excessive amount of ROS generation occurs in the ageing inner ear. The exact etiopathogenesis of presbycusis is not known, but it is generally accepted that it is the result of series of insults, such as physiologic age-related degeneration, noise exposure, medical disorders and their treatment, as well as hereditary susceptibility. The effect of aging shows a wide interindividual range; we aimed to investigate whether profiles of NAT2 genotypes may be associated with the risk of presbycusis. STUDY DESIGN: Hospital-based, case-control study. METHODS: We examined 68 adults with presbycusis and 98 healthy controls. DNA was extracted from whole blood, and the polymorphisms of NAT2*5A, NAT2*6A, NAT2*7A/B, and NAT2*14A were determined using a real-time polymerase chain reaction and fluorescence resonance energy transfer with a Light-Cycler Instrument. Associations between specific genotypes and the development of presbycusis were examined by use of logistic regression analyses to calculate odds ratios and 95% confidence intervals. RESULTS: Gene polymorphisms at NAT2*5A, NAT2*7A/B, and NAT2*14A in subjects with presbycusis were not significantly different from in the controls (P > .05). However, in NAT2*6A, the risk of presbycusis was 15.2-fold more in individuals with mutant allele than subjects with wild genotype (P = .013). Individuals with NAT2*6A heterozygote allele had a 0.34-fold less risk in the development of presbycusis than subjects with mutant allele (P = .032) CONCLUSION: We demonstrated a significant association between the NAT2*6A polymorphism and age-related hearing loss in this population. However, the sample size was relatively small, and further studies need to investigate the exact role of NAT2 gene polymorphism in the etiopathogenesis of the presbycusis.
Alleles↗
Presbycusis: a human temporal bone study of individuals with flat audiometric patterns of hearing loss using a new method to quantify stria vascularis volume.
OBJECTIVE: The purpose of this study was to determine the prevalence of stria vascularis atrophy in individuals with presbycusis and flat audiometric patterns of hearing loss. Individuals with presbycusis have historically been categorized by the shape of their audiograms, and flat audiometric thresholds have been reported to be associated with atrophy of the stria vascularis. Stria vascularis volume was not measured in these studies. STUDY DESIGN: Retrospective case review. METHODS: Archival human temporal bones from individuals with presbycusis were selected on the basis of strict audiometric criteria for flat audiometric thresholds. Six temporal bones that met these criteria were identified and compared with 10 temporal bones in individuals with normal hearing. A unique quantitative method was developed to measure the stria vascularis volume in these temporal bones. The hair cell and spiral ganglion cell populations also were quantitatively evaluated. RESULTS: Only one of the six individuals with presbycusis and flat audiometric thresholds had significant atrophy of the stria vascularis. This individual with stria vascularis atrophy also had reduced inner hair cell, outer hair cell, and ganglion cell populations. Three of the individuals with presbycusis had spiral ganglion cell loss, three individuals had inner hair cell loss, and all six individuals had outer hair cell loss. CONCLUSIONS: The results of this investigation suggest that individuals with presbycusis and flat audiometric patterns of hearing loss infrequently have stria vascularis atrophy. Outer hair cell loss alone or in combination with inner hair cell or ganglion cell loss may be the cause of flat audiometric thresholds in individuals with presbycusis.
Adult↗
Correlation between accelerated presbycusis and decreased immune functions.
The aim of the current study is to analyze the relationship between presbycusis and the immune system, which is affected by pathogenic environments, and to devise a strategy for the prevention of presbycusis using the SAMP1 mouse, an animal model for accelerated senescence that shows both immunological dysfunction and hearing loss caused by the impairment of spiral ganglion cells in the cochlea. When these mice were bred in different pathogenic environments, we found that the development of age-related diseases such as presbycusis was delayed in the mice bred under clean conditions. Prednisolone administration showed no significant prevention of the development of presbycusis in the mice, suggesting that autoimmune mechanisms are not involved in the acceleration of presbycusis. It is conceivable that pathogen-induced infections impose a severe stress on the host, impairing the host's immune functions. A reduction in the number of pathogens may therefore prevent the acceleration of the aging process. These findings suggest that not only the gene backgrounds but also immune functions affect the development of presbycusis in SAMP1 mice. Further studies into the relationship between systemic immune functions and the neuro-generation system may provide additional information about the treatment for age-related diseases.
Aging↗
Glutathione S-transferase gene polymorphisms in presbycusis.
HYPOTHESIS: Glutathione and glutathione-related antioxidant enzymes are involved in the metabolism and detoxification of cytotoxic and carcinogenic compounds as well as reactive oxygen species. Reactive oxygen species generation occurs in prolonged relative hypoperfusion conditions such as in aging. The etiology of presbycusis is much less certain; however, a complex genetic cause is most likely. The effect of aging shows a wide interindividual range; we aimed to investigate whether profiles of (glutathione S-transferase (GST) M1, T1 and P1 genotypes may be associated with the risk of age-related hearing loss. PATIENTS AND METHODS: We examined 68 adults with presbycusis and 69 healthy controls. DNA was extracted from whole blood, and the GSTM1, GSTT1 and GSTP1 polymorphisms were determined using a real-time polymerase chain reaction and fluorescence resonance energy transfer with a Light-Cycler Instrument. Associations between specific genotypes and the development of presbycusis were examined by use of logistic regression analyses to calculate odds ratios and 95% confidence intervals. RESULTS: Gene polymorphisms at GSTM1, GSTT1, and GSTP1 in subjects with presbycusis were not significantly different than in the controls (p > 0.05). Also, the combinations of different GSTM1, GSTT1, and GSTP1 genotypes were not an increased risk of presbycusis (p > 0.05). CONCLUSION: We could not demonstrate any significant association between the GSTM1, GSTT1, and GSTP1 polymorphism and age-related hearing loss in this population. This may be because of our sample size, and further studies need to investigate the exact role of GST gene polymorphisms in the etiopathogenesis of the presbycusis.
Adult↗
Presbycusis: a human temporal bone study of individuals with downward sloping audiometric patterns of hearing loss and review of the literature.
OBJECTIVE: The purpose of this retrospective case review was to identify patterns of cochlear element degeneration in individuals with presbycusis exhibiting downward sloping audiometric patterns of hearing loss and to correlate these findings with those reported in the literature to clarify conflicting concepts regarding the association between hearing loss and morphologic abnormalities. METHODS: Archival human temporal bones from individuals with presbycusis were selected on the basis of strict audiometric criteria for downward-sloping audiometric thresholds. Twenty-one temporal bones that met these criteria were identified and compared with 10 temporal bones from individuals with normal hearing. The stria vascularis volumes, spiral ganglion cell populations, inner hair cells, and outer hair cells were quantitatively evaluated. The relationship between the severity of hearing loss and the degeneration of cochlear elements was analyzed using univariate linear regression models. RESULTS: Outer hair cell loss and ganglion cell loss was observed in all individuals with presbycusis. Inner hair cell loss was observed in 18 of the 21 individuals with presbycusis and stria vascularis loss was observed in 10 of the 21 individuals with presbycusis. The extent of degeneration of all four of the cochlear elements evaluated was highly associated with the severity of hearing loss based on audiometric thresholds at 8,000 Hz and the pure-tone average at 500, 1,000, and 2,000 Hz. The extent of ganglion cell degeneration was associated with the slope of the audiogram. CONCLUSIONS: Individuals with downward-sloping audiometric patterns of presbycusis exhibit degeneration of the stria vascularis, spiral ganglion cells, inner hair cells, and outer hair cells that is associated with the severity of hearing loss. This association has not been previously reported in studies that did not use quantitative methodologies for evaluating the cochlear elements and strict audiometric criteria for selecting cases.
Adult↗
The relationship between presbycusis and mastoid pneumatization.
Presbycusis is defined as the natural hearing loss accompanying aging, caused by degenerative changes in the inner ear. The etiology of presbycusis is uncertain. However, it would appear that a complex genetic cause is most likely. The determinants of mastoid size continue to be controversial. One of the pneumatization theories is the hereditary theory. In this study, the possible relationship between presbycusis and the extent of mastoid pneumatization was investigated. This study was carried out on 21 patients with presbycusis and 21 normal subjects of similar ages. The pneumatized volume was measured by computerized tomography. The temporal bone was scanned at 2 mm thickness intervals. Exposure (kV 130, mA105). The scan plane was parallel to the orbitomeatal line and the CT images covered the entire mastoid region. The average mastoid pneumatization in presbycusis group was 6.08 +/- 2.52 cm(3) in the right ear and 6.19 +/- 2.93 cm(3) in the left ear. However, in the control group it was 4.69 +/- 3.17 cm(3) in the right ear (p=0.12) and 5.10 +/- 3.49 cm(3) in the left ear (p=0.28). No significant difference was found between the presbycusis patients and normal subjects in terms of the volume of mastoid pneumatization.
Aged↗
Mitochondrial DNA deletions associated with aging and possibly presbycusis: a human archival temporal bone study.
HYPOTHESIS: We attempted to determine if the common mitochondrial DNA aging deletion is also associated with presbycusis. BACKGROUND: Presbycusis is the most common cause of deafness in adults in the United States, affecting approximately 40% of the population older than 75 years of age. The ability to identify a gene(s) or a specific genetic deficit(s) associated with presbycusis has significant clinical importance. METHODS: The current study examined mitochondrial DNA (mtDNA) from cochlear sections of 34 human temporal bones: 17 with normal hearing and 17 with presbycusis. DNA was extracted from celloidin-embedded temporal bone sections; and specific oligonucleotide primers were designed to amplify the cytochrome b gene and a 4,977 base pair (bp) deletion of the mtDNA. Polymerase chain reaction (PCR) was used to amplify the base pair products that correspond to targeted gene regions, and sequencing was used to verify the products. RESULTS: Fourteen of the 17 patients with hearing loss showed the 4,977 bp deletion and this deletion was present in only eight of the 17 human specimens with normal audiograms. The cytochrome b gene was amplified from all specimens. CONCLUSIONS: The current study demonstrates the presence of a 4,977 bp deletion in human mitochondrial DNA genome that is associated with aging and with some forms of presbycusis. These results, coupled with previous animal studies, suggest that this 4,977 deletion may be associated with presbycusis.
Adult↗
Incidence of presbycusis of Korean populations in Seoul, Kyunggi and Kangwon provinces.
Presbycusis, a bilateral sensorineural hearing loss caused by changes in the inner ear, is related to multiple factors such as noise exposure and otologic disease. In institute-based studies, we tried to determine the incidence of presbycusis in Korean populations living in Seoul, Kyunggi and Kangwon provinces by gender and age groups. The subjects were people who had visited health promotion centers. Pure tone audiometry was done over 20 years on 6,028 subjects. In a community-based study, the subjects were elderly residents of Kanghwa-do area. There were no obvious factors that could cause hearing impairment in the subjects. For the pure tone audiometry, hearing threshold was obtained by using the six-dimension method. The incidence of presbycusis for subjects aged 65 years and older was 37.8% and 8.3% for > or = 27 dB HL criterion and > or = 41 dB HL criterion, respectively. The incidence increased with age. A statistically significant difference in the hearing threshold was found between men and women aged 65 years or older. No differences were found between the community-based study and the institute- based studies. There was a high incidence (about 40%) of presbycusis among Koreans aged 65 years or older (for > or = 27 dB HL criterion). With an aging population, we anticipate that this report could be used to provide a basic data for the study of presbycusis.
Adult↗
[Cochlear hypoxia and mtDNA deletion: possible correlated factors to cause presbycusis].
OBJECTIVE: To find the relationship among the most common mitochondrial DNA (mtDNA) 4,977 bp deletion, aging and deterioration of acoustic organ and determine the pathologic factors causing mtDNA 4,977 bp deletion. METHODS: Sixty-seven temporal bones from a presbycusis group, an age-matched control group and a young control group were evaluated. The nested PCR and tri-nested PCR techniques were used to test the presence of mtDNA 4,977 deletion. Computer imaging processing was used to measure the parameters of blood vessels in the internal acoustic meatus. RESULTS: Temporal bones from patients aged 50 years or over frequently showed mtDNA 4,977 deletions. In presbycusis patients, 17 of 34 ears showed mtDNA 4,977 deletion, whereas only 4 of 19 ears from the age-matched control group showed mtDNA 4,977 deletions. mtDNA 4,977 deletions were often seen in the spiral ganglion and vestibular ganglion neurons. In the presbycusis group, the lumen of the vasa nervosum of the internal auditory meatus showed a more severe reduction in patients with mtDNA 4,977 deletion than in those without deletion. CONCLUSION: There is a strong correlation between presbycusis and mtDNA 4,977 deletion. We hypothesize that cochlear hypoxia may cause mtDNA 4,977 deletions and other mtDNA mutants which in turn may cause a reduction of mitochondrial oxidative phosphorylation and decreased auditory nerve function. The symptoms of neural presbycusis, however, may appear only after mtDNA metabolism decreases below a specific threshold.
Aged↗
[Mitochondrial DNA4568 deletions in guinea-pig associated with presbycusis].
OBJECTIVE: To determine weather or not the mtDNA(4568) deletions in guinea-pig contribute to the development of presbycusis. METHODS: Forty-four guinea-pigs were divided into 2 groups: group A (young control group, normal hearing, 22 guineas) and group B (aged group). The group B was subdivided into group B(1) (old normal hearing, 6 guineas) and group B(2) (old hearing loss, 16 guineas). First the guineas were tested by auditory brainstem response (ABR), and then the Cortis's tissues, auditory nerve tissues, brain and blood were harvested and the total DNA was extracted. The mtDNA(4568) deletion was analyzed by PCR. RESULTS: Hearing loss was occurred with age. The mtDNA(4568) deletion incidence of aged group in all tissues was significant higher than that of young control group (P< 0.05). The incidence of mtDNA deletion in Cortis's and auditory nerve with presbycusis (B(2) group) were significant higher than that of aged normal hearing group (B(1) group) (P< 0.05). The incidence of mtDNA deletion in brain and blood was not significantly different between presbycusis and aged normal hearing group (P> 0.05). CONCLUSION: mtDNA(4568) deletion of guinea-pig possibly contributes to aging and mtDNA(4568) deletion in Cortis's and auditory nerve tissues of guinea-pig may be associated with presbycusis. There is no enough evidence to prove that the mtDNA(4568) deletions in brain and blood are related with presbycusis.
Age Factors↗
Hearing loss due to aging (presbycusis).
Presbycusis is the progressive hearing loss caused by histologic changes due to aging. Schuknecht described four histopathologic types of presbycusis and correlated these findings to audiometric data. In a retrospective study, some strict criteria were set to distinguish the "pure" cases of presbycusis in a group of 1,181 subjects, 50 years of age and older, seen in our Audiology Clinic over one year; 91 subjects were found to meet these criteria. An attempt was made to fit the pure tone threshold curves into the types described by Schuknecht and correlate these curves to speech discrimination, tone decay, recruitment, age and sex of these subjects. It was found that: (a) only 50% of these audiograms could be fitted into the described histopathologic types, suggesting that in 50% of the subjects, presbycusis was caused by more than one degenerative process; (b) in 86% of subjects, speech discrimination was excellent or good in quiet; this test therefore may not reflect the difficulties presbycusis have in understanding speech under adverse auditory conditions; (c) subjects with flat pure tone threshold curves had generally good discrimination; (d) no differences were found between males and females; and (e) tests for tone decay and recruitment showed that in most cases the hearing loss was due to cochlear pathology, but these data do not exclude the possibility of central auditory involvement.
Age Factors↗
The functional age of hearing loss in a mouse model of presbycusis. I. Behavioral assessments.
Presbycusis is a common form of hearing loss that progresses from high to low frequencies with advancing age. C57BL/6J mice experience a rapid progression of presbycusis-like hearing deficits and thus provide a convenient animal model for evaluating behavioral, physiological and anatomical correlates of the disorder. Previous studies of C57BL/6J mice have relied on short-term observations of age-matched subject groups to reconstruct a time course for auditory pathologies. Such statistical approaches are weakened by the variability of hearing thresholds in young mice and the inconsistent timing of degenerative effects in older mice. The present study was designed to resolve these ambiguities by tracking the hearing abilities of individual C57BL/6J mice from age 16 weeks until the onset of hearing loss in specific listening conditions. Testing at frequencies of 8 and 16 kHz in quiet confirmed the high-to-low frequency progression that is characteristic of presbycusis. Often the hearing loss developed in two phases, one gradual and the other abrupt. Testing in noise revealed deficits that were first manifested as threshold instability and then an increased susceptibility to masking. These changes occurred before hearing loss in quiet. CBA/CaJ mice did not show significant loss during a similar period of observation. Our findings provide a well-ordered chronology for isolating the functional consequences of multiple cochlear pathologies that arise during the time course of presbycusis. This neurobehavioral assessment is termed the functional age of hearing loss. Neuroanatomical assessments of behaviorally characterized C57BL/6J mice are presented in the companion paper [Hear. Res. 183 (2003) 29-36].
Acoustic Stimulation↗
Temporal bone analysis of patients with presbycusis reveals high frequency of mitochondrial mutations.
Presbycusis is a histologically and genetically heterogenous group of disorders, which lead to progressive, primarily sensorineural hearing loss with aging. Acquired mitochondrial DNA defects have been proposed as important determinants of aging, particularly in neuro-muscular tissues. The spiral ganglion and membranous labyrinth from archival temporal bones of 5 patients with presbycusis were examined for mutations within the mitochondrially-encoded cytochrome oxidase II gene. When compared to controls, results indicate that mitochondrial mutations in the peripheral auditory system occur commonly with age-related hearing loss, that there is great individual variability in both quantity and location of mutation accumulation, and that at least a proportion of presbycusis patients have a highly significant load of mutations in auditory tissue. This work supports the hypothesis that acquired mitochondrial mutations are a determinant of hearing loss in a subgroup of presbycusis patients.
Aged↗
Differentiation of types of presbycusis using the masking-level difference.
Masking-level differences in quiet at 500 Hz were used to demonstrate evidence of elevated noise levels within the auditory systems of subjects with assumed neural presbycusis. The following five groups of subjects were evaluated: normal-hearing young and old adults; and older adults with metabolic, sensory, or neural presbycusis. The group with assumed neural presbycusis--that is, bilateral high-frequency sensorineural hearing loss and poor word-recognition performance--had masking-level differences (a) in quiet that were significantly larger than those for the other groups and (b) in noise that were significantly smaller than those for the other groups. The data suggest that elevated internal noise levels accompany neural presbycusis.
Adolescent↗
Comparisons between the median hearing threshold levels for an unscreened black nonindustrial noise exposed population (NINEP) and four presbycusis data bases.
The median hearing threshold level (HTL) data representing an unscreened black nonindustrial noise exposed population (NINEP) are compared to the median HTL data of three previously established presbycusis data bases by Hinchcliffe, Corso, and Rosen, and the data base developed by Robinson and Sutton. The data bases are all normalized relative to age 18. Comparisons are made between the black NINEP and the presbycusis data base HTLs for different sex and age groupings. The unscreened black NINEP exhibits median HTLs similar to those of the presbycusis data bases for ages less than approximately 35-45 years. However, for age groupings greater than 35-45 years, the median HTLs of the black NINEP are generally lower (better hearing) than those of the referenced presbycusis data bases even though this data base exhibited significant nonindustrial noise exposures, and medical and pathological problems which were not screened out of the population.
Adult↗