Interactive effects of hearing aid use and cognitive function in patients with hearing loss.

BACKGROUND: There has been a significant increase in scientific investigations of the hearing-dementia association among the research on potentially modifiable risk factors for cognitive impairment. We tested two clinical questions. Analysis 1: does persistent hearing aid (HA) use decrease the decline in cognitive function caused by ageing? Analysis 2: does cognitive function at the time of HA fitting predict future persistent HA use? METHODS: This case-control study performed at two referral centres reported data obtained over a 4.5-year period. We recruited a group of patients with cognitive decline, aged 65 or older with or without hearing loss. The intervention consisted of the use of HAs. The primary outcome measures were adherence to continuous HA use and cognitive function measured using the Japanese version of the Mini-Mental State Examination Test and the Reading Cognitive Test Kyoto. RESULTS: Eighteen HA users and 18 controls were included in the first analysis. HA use was associated with a deceleration of cognitive decline 12 months later. In the second analysis, 11 participants with good adherence to HA use were compared with 12 participants who showed poor adherence to HA use. Among the variables employed in this study, cognitive function measured using the Reading Cognitive Test Kyoto was significantly lower in participants with poor adherence to HA. CONCLUSIONS: HA use in cognitively impaired individuals with hearing loss can slow age-related cognitive decline. Cognitively impaired people with hearing loss who fail to commit to HA use tend to have lower cognitive measurement scores before HA fitting. HA use is generally more challenging as people age and their cognitive abilities decline. Therefore, it is desirable that HAs be used when hearing loss and dementia are in their early stages.

Pharmacokinetics of monoclonal antibodies locally-applied into the middle ear of guinea pigs.

Countless therapeutic antibodies are currently available for the treatment of a broad range of diseases. Some target molecules of therapeutic antibodies are involved in the pathogenesis of sensorineural hearing loss (SNHL), suggesting that SNHL may be a novel target for monoclonal antibody (mAb) therapy. When considering mAb therapy for SNHL, understanding of the pharmacokinetics of mAbs after local application into the middle ear is crucial. To reveal the fundamental characteristics of mAb pharmacokinetics following local application into the middle ear of guinea pigs, we performed pharmacokinetic analyses of mouse monoclonal antibodies to FLAG-tag (FLAG-mAbs), which have no specific binding sites in the middle and inner ear. FLAG-mAbs were rapidly transferred from the middle ear to the cochlear fluid, indicating high permeability of the round window membrane to mAbs. FLAG-mAbs were eliminated from the cochlear fluid 3 h after application, similar to small molecules. Whole-body autoradiography and quantitative assessments of cerebrospinal fluid and serum demonstrated that the biodistribution of FLAG-mAbs was limited to the middle and inner ear. Altogether, the pharmacokinetics of mAbs are similar to those of small molecules when locally applied into the middle ear, suggesting the necessity of drug delivery systems for appropriate mAb delivery to the cochlear fluid after local application into the middle ear.

Efficient Bone Conduction Hearing Device With a Novel Piezoelectric Transducer Using Skin as an Electrode.

OBJECTIVE: Bone conduction hearing aids are the only non-surgical devices used for conductive hearing loss. However, they are impractical for lifelong use since they require close contact of the transducer with the head skin, causing skin erosion and discomfort. Bone conduction hearing implants and active middle ear implants do not present these issues; however, they require surgery and can sometimes cause issues in the skin surrounding the devices. This study aimed to develop a new bone conduction hearing device that does not exert pressure on the skin or require surgery. METHODS: Our device modified a piezoelectric element by using the skin of a pinna as one of the two electrodes of a conventional piezoelectric device. We compared the sound transmission of a speaker, a conventional piezoelectric device, or the new device to the Guinea pig cochlea, a physiological sound transducer to the auditory nerve, in normal and air-conductive hearing loss conditions. RESULTS: The novel device transmitted sound to the cochlea even after causing air-conductive hearing loss. Its bone conduction was more efficient than the speaker and the conventional piezoelectric device. CONCLUSION: We developed a novel type of bone conduction device that efficiently transmits sound to the cochlea by skipping the external auditory canal, tympanic membrane, and middle ear ossicles. This device does not exert pressure on the skin that can result in skin damage, an adverse effect of a conventional bone conduction hearing aid. SIGNIFICANCE: Our novel hearing device can be used as a substitute for current bone-conduction hearing devices.

Development of the Reading Cognitive Test Kyoto (ReaCT Kyoto) for Early Detection of Cognitive Decline in Patients with Hearing Loss.

BACKGROUND: Early detection of cognitive decline allows timely intervention to delay progression of dementia. However, current cognitive evaluation tools often include items delivered via verbal forms of instruction, which can cause poor performance in patients with hearing loss. OBJECTIVE: To develop and validate a cognitive screening battery, the Reading Cognitive Test Kyoto (ReaCT Kyoto), comprising test items given through non-verbal instruction. METHODS: A cross-sectional and multi-center study was conducted in the three medical institutes. ReaCT Kyoto was designed to evaluate domains of "registration," "repetition," "delayed recall," "visuospatial recognition," "orientation in time and place," and "executive function." The Japanese version of the Mini-Mental State Examination Test (MMSE-J) and ReaCT Kyoto were applied by experienced psychotherapists. Concurrent validity was evaluated between the ReaCT Kyoto Test and MMSE-J and between the ReaCT Kyoto Test and physician-diagnosed dementia. RESULTS: ReaCT Kyoto was validated in a sample of 115 participants. The mean age of subjects was 81.0±6.4 years, and the sample comprised 53.0% females. The area under the receiver operating curves was 0.95 for detecting physician-diagnosed dementia. When classifying patients in accordance with presence or absence of hearing loss, the AUCs were 0.93 and 0.97 for those with and without hearing loss, respectively. With a cut-off score of < 29 points for suspected dementia, ReaCT Kyoto correctly classified 90.4% of the subjects as belonging to the group with or without physician-diagnosed dementia. CONCLUSION: ReaCT Kyoto provides an appropriate solution for detection of cognitive impairment in persons with or without hearing loss.

Hearing preservation at low frequencies by insulin-like growth factor 1 in a guinea pig model of cochlear implantation.

The hybrid or electric-acoustic stimulation cochlear implant is indicated in patients with a residual hearing at low frequencies. It provides electric and acoustic stimulation for compensating for high- and low-frequency sounds, respectively. However, the implantation procedure damages the cochlea, resulting in loss of the residual-hearing and diminished effects of the acoustic-hearing in several patients. To prevent hearing loss after implantation, corticosteroids have been used clinically although their effects are limited. As an alternative to corticosteroids, insulin-like growth factor 1 (IGF1) has shown potent effects in various types of cochlear injury. In this study, the effects of IGF1 on hearing preservation were examined after cochlear implantation to a normal-hearing guinea pig model. The electrode was inserted in an atraumatic way through the round window membrane of guinea pigs with the application of a gelatin-sponge soaked with IGF1 or saline. The auditory brainstem response (ABR) was recorded pre-operatively, immediately after cochlear implantation, and 7, 14, 28, and 56 days after electrode insertion. In comparison to the control group, the IGF1-treated group showed better hearing preservation at low frequencies, 7 days after surgery. IGF1 application was effective at low frequencies (2 and 4 kHz) throughout the period of examination. Histological studies revealed that outer hair cell numbers, in the IGF1-treated group, were maintained in the cochlear region responsible for low-frequency hearing (upper midbasal turn) and that there was less fibrous tissue formation around the electrode. Both the outer hair cell counts and the extent of fibrosis significantly correlated with the ABR threshold shifts at low frequencies. These results indicate that IGF1 might attenuate loss of low-frequency hearing after cochlear implantation, suggesting its possible clinical use in soft surgeries involving cochlear implants with electric-acoustic stimulation for hearing preservation.