Since there is, at present, no established therapy against noise-induced hearing loss, it is important to take actions to minimize exposure to harmful levels of noise by reducing the noise itself and the exposure time, and by promoting the use of ear plugs. It is also important to perform auditory controls. Although auditory controls or medical checkups are commonly performed in noisy workplaces in Japan, the control techniques are unsatisfactory. In October 1992, the Ministry of Labour issued “Guidelines for Preventing Noise-Induced Disorders” based on the trend for noise exposure criteria in foreign countries. The guidelines obligate employers to take actions to prevent noise-induced disorders at workshops workplaces with noise levels equivalent to 85 dB (A) or higher. This paper reports the guidelines in terms of the definition of noisy workplaces, preventive measures against noise-induced disorders, prevention of hearing loss, and hearing conservation.
This study was aimed at investigating the relationship between the age at cochlear implantation (CI) and language development using a set of Japanese language assessment test battery, consisting of communication skills testing, vocabulary testing, and syntax testing. Of the 638 hearing-impaired children enrolled, 182 children (83 males and 99 females) with CI were included in this study. They were fitted with their first hearing aids (HA) at 27 months and underwent CI at 42 months, on average. Subjects were classified into four groups according to the age at CI and at the first fitting of HA, as follows: 1) early CI and HA group, 2) early HA and delayed CI group, 3) early CI and delayed HA group, 4) delayed CI and HA group. Our study showed that early cochlear implantation was beneficial for the development of productive vocabulary and syntax, and early fitting of HA was beneficial for the development comprehensive vocabulary and syntax. We concluded that early auditory input is effective for the development of language comprehension, and early development of speech discrimination is effective for the development of language production.
To determine the influence of diabetes-related factors on hearing, we analyzed the data of 90 middle-aged and older patients who were participating in an inpatient diabetes education program at the National Center for Geriatrics and Gerontology. Statistical analysis was performed to identify factors associated with the hearing level for 9 frequencies using stepwise multiple regression; the independent variables included in the statistical model were age, sex, history of lifestyle-related diseases, smoking history, history of insulin usage, diabetes duration, fasting blood glucose level on admission, HbA1c, serum creatinine, creatinine clearance, diabetic retinopathy, history of ear diseases, and occupational noise exposure. Among the diabetes-related factors, history of insulin usage was found to have a statistically significant detrimental effect on hearing over a wide frequency range. Comparison of the groups with and without a history of insulin usage revealed significant elevation of the hearing thresholds at 1000, 2000 and 3000 Hz in the group with a history of insulin usage . The impact of diabetes on hearing was discussed was discussed in the context of previous epidemiological studies, histopathological analyses and reported hypothetical mechanisms.
We investigated the relation between the hearing threshold and the age at cochlear implantation, duration of deafness, and cause of deafness in 45 adult long-term cochlear implant users. We compared the T level and C level, dynamic range, and speech perception between the group with a good hearing threshold (the good group) and the group with a poor hearing threshold (the poor group). The results were as follows. 1.A tendency towards a good hearing threshold was observed in cases with a duration of deafness of one year or less. 2.Significant differences in the C level and consonant perception scores were observed between the good group and the poor group. 3.The results suggested a high hearing threshold and low consonant perception scores in the poor group, because it was difficult to raise the C level and T level, and to widen the dynamic range. 4.The findings suggested the possibility that the degeneration of the auditory nerve fibers on the retrocochlear auditory pathway caused a high hearing threshold in the poor group. 5.The findings also suggested the possibility that a disturbed retrocochlear auditory pathway affected the hearing threshold and the consonant perception scores.
It is sometimes difficult to fit hearing aids (HA) in children with mild-to-moderate hearing impairment sufficiently early in life, and one of the reasons is the economic problem. A unique subsidy system for purchase of HA was started in Mie prefecture in 2006 for infants with mild-to-moderate hearing impairment. We examined the data of 100 children who were newly fitted with HA at the Mie Child Guidance Center over five years. Thirty-six of the 59 children with mild-to-moderate hearing impairment purchased HA through using this subsidy (“subsidy group”). The remaining 23 of the 59 children could not use the subsidy system because of the limitation of age, hearing level, or income restriction (“non-subsidy group”). The 41 patients with severe hearing impairment were supplied with HA as mandated by the National law (“National-support group”). The ages at diagnosis and at obtaining the HA were significantly lower in the subsidy group and National-support group than in the non-subsidy group. The interval from diagnosis to being fitted with HA was significantly longer in the subsidy group than in the National-support group. This result suggests that it takes time for the family to accept hearing loss in an infant and that the financial burden is still greater in the subsidy group. In the subsidy group, HA were used appropriately. Deregulation of the system with increase of the subsidy is required.