Effect of hearing aids on body balance function in non-reverberant condition: A posturographic study.

OBJECTIVE: The purpose of this study was to evaluate the effect of hearing aids on body balance function in a strictly controlled auditory environment. METHODS: We recorded the findings of 10 experienced hearing aid users and 10 normal-hearing participants. All the participants were assessed using posturography under eight conditions in an acoustically shielded non-reverberant room: (1) eyes open with sound stimuli, with and without foam rubber, (2) eyes closed with sound stimuli, with and without foam rubber, (3) eyes open without sound stimuli, with and without foam rubber, and (4) eyes closed without sound stimuli, with and without foam rubber. RESULTS: The auditory cue improved the total path area and sway velocity in both the hearing aid users and normal-hearing participants. The analysis of variance showed that the interaction among eye condition, sound condition, and between-group factor was significant in the maximum displacement of the center-of-pressure in the mediolateral axis (F [1, 18] = 6.19, p = 0.02). The maximum displacement of the center-of-pressure in the mediolateral axis improved with the auditory cues in the normal-hearing participants in the eyes closed condition (5.4 cm and 4.7 cm, p < 0.01). In the hearing aid users, this difference was not significant (5.9 cm and 5.7 cm, p = 0.45). The maximum displacement of the center-of-pressure in the anteroposterior axis improved in both the hearing aid users and the normal-hearing participants.

Characteristics of Lower Limb Muscle Activity in Elderly Persons After Ergometric Exercise.

This study examined the characteristics of lower limb muscle activity in elderly persons after ergometric pedaling exercise for 1 month. To determine the effect of the exercise, surface electromyography (SEMG) of lower limb muscles was subjected to Daubechies-4 wavelet transformation, and mean wavelet coefficients were compared with the pre-exercise coefficients and the post-exercise coefficients in each wavelet level. The characteristics of muscle activity after pedaling exercise were also compared between the elderly subjects and young subjects. For the elderly subjects, the mean wavelet coefficients were significantly decreased in the tibialis anterior and the gastrocnemius medialis at wavelet levels of 3, 4, and 5 (125-62.5, 62.5-31.25, and 31.25-15.625 Hz, respectively), by pedaling exercise. However, the mean power of wavelet levels of 2 and 3 (250-125 and 125-62.5 Hz) within the rectus femoris and the biceps femoris were significantly increased in the young subjects. The effect of pedaling exercise is different from the effects of heavy-resistance training. It was suggested that the muscle coordination, motor unit (MU) firing frequency, and firing fiber type of lower limb muscles are changed with the different characteristics between elderly and young persons by pedaling exercise for 1 month.

Body balance function of cochlear implant patients with and without sound conditions.

OBJECTIVE: The relation between well-controlled auditory stimulation through cochlear implant (CI) and the body balance has been sparsely investigated. The purpose of this study was to evaluate the body balance function of CI patients with- and without-sound in anechoic sound-shielded room. METHODS: We recorded 8 experienced CI recipients and 8 young normal-hearing volunteers. All subjects were assessed using posturography under 4 conditions: (1) eyes open with-sound, (2) eyes closed with-sound, (3) eyes open without-sound, and (4) eyes closed without-sound. RESULTS: The total path length and the total area were significantly larger in the eyes closed condition than in the eyes open condition. In normal hearing subjects, the average displacement of center of pressure (COP) in the mediolateral direction under with-sound condition was not different from that under without-sound condition. In CI recipients, the COP significantly displaced to the CI side after the deprivation of visual cues in without-sound condition. This shift was eliminated in with-sound condition (significant interaction among sound condition, eye condition, and between-group factor). CONCLUSION: In CI subjects, sound stimulation improves the abnormal displacement of COP in the mediolateral direction. SIGNIFICANCE: A posturographic study under an anechoic condition proved that sound stimulation improves body balance function in CI subjects.

Estimation of Japanese international financial assistance for HIV/AIDS control for 2003-2007: difficulties and limitations of data collection.

The purpose of this paper is to: (1) collect relevant data and estimate Japanese international financial assistance for HIV/AIDS control; (2) discuss the difficulties in collecting relevant data and the limitations of the collected data; and (3) conduct a comparative analysis on the estimated data with OECD and Kaiser Family Foundation aggregate data. The point is that we have comprehensively collected and estimated the data on Japanese international expenditures for HIV/AIDS control while there is no reliable data that is totally managed and published. In addition, we discuss the difficulties and limitations of data collection: unpublished data; insufficient data; inseparable data; problems of exchange rates; gaps between disbursement and commitment; and difference in year period among calendar, fiscal and organization-specific years. Furthermore, we show the risk of underestimating the Japanese international contribution to HIV/AIDS control on the basis of OECD and Kaiser data. In this respect, it is significant to comprehensively collect and estimate the data on Japanese international assistance for HIV/AIDS control. Finally, we derive the implication that it is crucial for a relevant international organization and/or individual countries to comprehensively collect and administer data for international cooperation in the development of health policies for HIV/AIDS.

Evaluation method for hearing aid fitting under reverberation: comparison between monaural and binaural hearing aids.

Some hearing-impaired persons with hearing aids complain of listening difficulty under reverberation. No method, however, is currently available for hearing aid fitting that permits evaluation of hearing difficulty caused by reverberations. In this study, we produced speech materials with a reverberation time of 2.02 s that mimicked a reverberant environment (a classroom). Speech materials with reverberation times of 0 and 1.01 s were also made. Listening tests were performed with these materials in hearing-impaired subjects and normal-hearing subjects in a soundproof booth. Listening tests were also done in a classroom. Our results showed that speech material with a reverberation time of 2.02 s had a decreased listening-test score in hearing-impaired subjects with both monaural and binaural hearing aids. Similar results were obtained in a reverberant environment. Our findings suggest the validity of using speech materials with different reverberation times to predict the listening performance under reverberation of hearing-impaired persons with hearing aids.