Folate supplementation and age-related hearing loss.
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Aged↗
Biomedical subjects
Robert A Dobie
Publications and source records attributed to Robert A Dobie.
Hearing loss in patients with vestibulotoxic reactions to gentamicin therapy.
OBJECTIVES: To determine whether patients with vestibulotoxic reactions to gentamicin have hearing thresholds worse than predicted by distributions of better-ear hearing thresholds in people of the same age and sex in the general population, and, if so, to measure the severity and audiometric pattern of that hearing loss. DESIGN: Retrospective case series from previously published prospective and retrospective studies of vestibular function in patients receiving gentamicin. SETTING: Tertiary neurotological practice. PATIENTS: Convenience sample of 33 consecutive patients seen for objective evidence of vestibulotoxic reactions after systemic gentamicin therapy. Twenty-five of 33 patients underwent valid and complete audiometry. MAIN OUTCOME MEASURES: Age- and sex-corrected better-ear pure tone thresholds, 0.5 to 6.0 kHz. The better-ear audiogram was defined in 2 ways: primarily, the audiogram of the ear with the better average threshold at 0.5, 1.0, and 2.0 kHz; secondarily, the composite audiogram taking the better threshold for each frequency. RESULTS: Patients exhibiting vestibulotoxic reactions to gentamicin therapy had hearing thresholds that were similar to those seen in the general population at 0.5, 3.0, and 6.0 kHz. Median thresholds were 6 to 7 dB worse than expected at 1.0 and 2.0 kHz (95% confidence intervals, 2-13 dB and 3-12 dB, respectively). The largest median difference was 15 dB at 4.0 kHz (95% confidence interval, 3-23 dB), but this difference was not significant for the more conservative composite definition of the better ear. CONCLUSIONS: Patients with vestibulotoxic reactions to gentamicin therapy have little additional hearing loss compared with the general population. Physicians should monitor both auditory and vestibular function when aminoglycosides, especially gentamicin, must be used.
Adult↗
Methodological issues when comparing hearing thresholds of a group with population standards: the case of the ferry engineers.
OBJECTIVES: To discuss appropriate and inappropriate methods for comparing distributions of hearing thresholds of a study group with distributions in population standards and to determine whether the thresholds of Washington State Ferries engineers are different from those of men in the general population, using both frequency-by-frequency comparisons and analysis of audiometric shape. DESIGN: The most recent hearing conservation program audiograms of 321 noise-exposed engineers, ages 35 to 64, were compared with the predictions of Annexes A, B, and C from ANSI S3.44. There was no screening by history or otoscopy; all audiograms were included. 95% confidence intervals (95% CIs) were calculated for the engineers' median thresholds for each ear, for the better ear (defined two ways), and for the binaural average. For Annex B, where 95% CIs are also available, it was possible to calculate z scores for the differences between Annex B and the engineers' better ears. Bulge depth, an audiometric shape statistic, measured curvature between 1 and 6 kHz. RESULTS: Engineers' better-ear median thresholds were worse than those in Annex A but (except at 1 kHz) were as good as or better than those in Annexes B and C, which are more appropriate for comparison to an unscreened noise-exposed group like the engineers. Average bulge depth for the engineers was similar to that of the Annex B standard (no added occupational noise) and was much less than that of audiograms created by using the standard with added occupational noise between 90 and 100 dBA. CONCLUSIONS: Audiograms from groups that have been selected for a particular exposure, but, without regard to severity, can appropriately be compared with population standards, if certain pitfalls are avoided. For unscreened study groups with large age-sex subgroups, a simple method to assess statistical significance, taking into consideration uncertainties in both the study group and the comparison standard, is the calculation of z scores for the proportion of better-ear thresholds above the Annex B median. A less powerful method combines small age-sex subgroups after age correction. Small threshold differences, even if statistically significant, may not be due to genuine differences in hearing sensitivity between study group and standard. Audiometric shape analysis offers an independent dimension of comparison between the study group and audiograms predicted from the ANSI S3.44 standard, with and without occupational noise exposure. Important pitfalls in comparison to population standards include nonrandom selection of study groups, inappropriate choice of population standard, use of the right and left ear thresholds instead of the better-ear threshold for comparison to Annex B, and comparing means with medians. The thresholds of the engineers in this study were similar to published standards for an unscreened population.
Adult↗
Audiogram notches in noise-exposed workers.
OBJECTIVES: Diagnostic criteria for noise-induced hearing loss include the audiometric notch, yet no standardized definition exists. This study tested whether objective notch metrics could match the clinical judgments of an expert panel. DESIGN: A panel of occupational physicians, otolaryngologists, and audiologists reviewed audiograms of noise-exposed workers. In a two-sample process, the panel judged whether a notch was present and whether hearing loss had progressed in a notch pattern. Quantitative notch metrics were compared against expert decisions. RESULTS: At least five of six experts agreed about notch identification in 71 and 72% of the cases in the two samples, and agreement about notch progression was 61 and 67%. Notch depth and professional specialty appeared to affect notch judgments. Despite this variability, a notch metric showed excellent agreement with expert notch consensus in each sample (94.7 and 96.6%; kappa = 0.88 and 0.92). CONCLUSIONS: Audiogram notch metrics can agree with expert clinical consensus and assist in the surveillance of noise-exposed workers.
Adult↗
Audiometric threshold shift definitions: simulations and suggestions.
OBJECTIVES: Determine (1) whether pure-tone average (PTA) or "any frequency" (AF) definitions of significant threshold shift (STS) are more accurate under different conditions; (2) whether STS definitions applied twice are more accurate than when applied once; (3) whether three surrogate analysis methods applicable to real-world audiometric data can appropriately measure the accuracy of STS definitions; and (4) whether evidence from previous studies supports a change in the current STS definition used by the Occupational Safety and Health Administration (OSHA); (5) make recommendations for future research. DESIGN: Computer simulation of periodic audiograms, with typical test-retest variability, from seven groups of individuals (N = 1000 each), with or without threshold shifts of different sizes at different frequencies; receiver operating characteristic area analysis to determine relative accuracy of PTA and AF decision variables, applied once or twice; testing of surrogate methods (confirmation, variability, and comparison) against receiver operating characteristic areas in estimation of accuracy of decision variables; review of previous studies, considering the limitations of the surrogate methods that were used. RESULTS: Either AF or PTA definitions may be preferable, depending on whether the genuine threshold shift has occurred at a single frequency or across a range of frequencies. Including too few or too many frequencies degrades the performance of both AF and PTA variables. An STS decision variable performs only slightly better when applied twice than when applied once. The surrogate methods can be useful, but all have important caveats: The comparison method is best, but only when an appropriate control group is available; the variability method is intermediate but requires that each decision variable be tested at multiple criterion values for reliable results. The confirmation method, which was the least accurate in assessing true performance, also requires testing at multiple levels. Even when this is done, it markedly exaggerates the benefit of applying an STS definition twice and makes STS definitions that identify large numbers of individuals falsely appear to be more accurate than definitions that identify smaller numbers of individuals. Taking these caveats into account, previous studies do not offer convincing evidence for a change in the current OSHA STS definition. CONCLUSIONS: Choice of an STS definition requires three judgments that cannot be made based on the type of analysis discussed in this report: The range of frequencies to be tested, whether to require that an STS definition be applied twice, and the acceptable magnitude of false-positive error. Once these judgments have been made, the techniques discussed here can assist in selecting the appropriate decision variable (typically PTA or AF) and a criterion value that yields an acceptable false-positive rate. Additional research using the techniques described in this report with either new or old audiometric databases could help determine whether any STS definition is significantly better than the current OSHA definition.
Audiometry, Pure-Tone↗
Estimating noise-induced permanent threshold shift from audiometric shape: the ISO-1999 model.
OBJECTIVE: To describe the relation between audiometric shape and noise-induced permanent threshold shift averaged across the speech frequencies (N5123). DESIGN: Using an international standard (ISO-1999), 270 audiograms were created, representing both sexes and a variety of ages, exposure levels, and percentiles. Bulge depth (BD) was defined as the difference between pure-tone average for 2, 3, and 4 kHz and PTA for 1 and 6 kHz. RESULTS: N5123 was well-predicted by quadratic functions of BD, which accounted for 72 to 95% of the variance in N5123. CONCLUSIONS: Estimates of N5123, based on BD, can be helpful in medical-legal diagnosis and allocation of hearing loss.
Adult↗
Depression and tinnitus.
Most patients with tinnitus are neither depressed nor seriously bothered by their tinnitus. Patients who complain bitterly of tinnitus, however, are often found to have a MDD. Treatment with tricyclic antidepressant drugs helps these patients, especially those who complain of insomnia. Other types of drugs and psychotherapy may also be helpful.
Depressive Disorder↗
A multi-center, double blind clinical trial comparing benefit from three commonly used hearing aid circuits.
OBJECTIVE: Although numerous studies have demonstrated that hearing aids provide significant benefit, carefully controlled, multi-center clinical trials have not been conducted. A multi-center clinical trial was conducted to compare the efficacy of three commonly used hearing aid circuits: peak clipping, compression limiting, and wide dynamic range compression. DESIGN: Patients (N = 360) with bilateral, sensorineural hearing loss were studied using a double blind, three-period, three-treatment crossover design. The patients were fit with each of three programmable hearing aid circuits. Outcome tests were administered in the unaided condition at baseline and then after 3 mo usage of each circuit, the tests were administered in both aided and unaided conditions. The outcome test battery included tests of speech recognition, sound quality and subjective scales of hearing aid benefit, including patients' overall rank-order rating of the three circuits. RESULTS: Each hearing aid circuit improved speech recognition markedly, with greater improvement observed for soft and conversationally loud speech in both quiet and noisy listening conditions. In addition, a significant reduction in the problems encountered in communication was observed. Some tests suggested that the two compression hearing aids provided a better listening experience than the peak clipping hearing aid. In the rank-order ratings, patients preferred the compression limiting hearing aid more frequently than the other two hearing aids. CONCLUSIONS: The three hearing aid circuits studied provide significant benefit both in quiet and in noisy listening situations. The two compression hearing aids appear to provide superior benefits compared to the linear circuit, although the differences between the hearing aids were smaller than the differences between unaided and aided conditions.
Aged↗
Subjective measures of hearing aid benefit in the NIDCD/VA Clinical Trial.
OBJECTIVE: Subjective measures of performance were assessed on three different hearing aid circuits as part of a large clinical trial. These measurements included the Profile of Hearing Aid Performance and a subjective ranking of individual preference. DESIGN: A multi-center, double-masked clinical trial of hearing aids was conducted at eight VA Medical Centers. Three hearing aid circuits, a linear peak-clipper, a linear compression limiter and a wide dynamic range compressor, were investigated. The experimental design was a three-period, three-treatment crossover design. Subjects (N = 360) were stratified by site and randomized to one of six sequences for the hearing aid circuits. All fittings were binaural and involved a 3-mo trial with each of the three circuits. All subjective measures were administered for unaided and aided conditions at the end of each trial period. RESULTS: While all of the circuits resulted in improved scores on the aided versus the unaided PHAP, there were few conditions in which one circuit outperformed the others. An exception was the aversiveness of sound subscale where the peak clipper frequently scored worse than either the compression limiter or the wide dynamic range compressor. In the subjective ranking scale the compression limiter received more first place rankings than the other two circuits, especially for one subgroup of patients with moderate flat hearing loss. CONCLUSIONS: All circuits were perceived as beneficial by these subjects in most situations. The peak clipper scored worse on aversiveness of sound than did the other two circuits for most subjects, while the compression limiter seemed to have a slight advantage in subjective rankings. Most subjects perceived considerable aided benefit in situations involving background noise and reverberation, situations where hearing aid benefit is often questioned.
Cross-Over Studies↗
Can posturography identify informed malingerers?
OBJECTIVE: This study evaluated whether information about computed dynamic posturography given to subjects instructed to feign vestibular impairment (malingerers) improved their attempts to display test patterns consistent with vestibular weakness. STUDY DESIGN: The study design was prospective, with blinded scoring of tests. SETTING: The study was conducted at a university hospital. PATIENTS: Sixty volunteer subjects, 20 to 59 years old, were randomly assigned to one of two equal groups: naïve subjects and subjects informed about computed dynamic posturography. INTERVENTIONS: Computed dynamic posturography was performed twice. First, subjects were instructed to feign a vestibular weakness. Second, subjects were instructed to perform the test normally. One group was given additional information about computed dynamic posturography before the first test (informed faking). MAIN OUTCOME MEASURES: The computed dynamic posturography test summaries were scored as normal, aphysiologic, or vestibular by two methods: the scoring method published by Cevette et al. in 1995 and blinded clinical scoring. The computed dynamic posturography test summaries of patients referred for vestibular disorders were included with the test summaries collected from subjects during scoring. These additional tests of possible "true" vestibular disorder allowed evaluation of scoring accuracy. RESULTS: The scoring method of Cevette et al. classified about one-third of the test results of feigned vestibular weakness as either normal (16.7%) or vestibular weakness (18.3%). The remaining two thirds of the test results of feigned vestibular weakness were classified as aphysiologic (65.0%). Blinded clinical scoring gave similar figures. Additional information about computed dynamic posturography did not increase the number of feigned test results scored as a vestibular weakness. CONCLUSION: When additional information about computed dynamic posturography was provided, the subjects did not improve their ability to feign vestibular weakness. This investigation supports the use of scoring computed dynamic posturography results by the formulae of Cevette et al. in separating aphysiologic behavior from vestibular impairment.
Adult↗