聴力の生理的年令変化について

抄録

It has been well known that the hearing acuity of healthy persons become worse with the increasef age (so-called physiological hearing loss by age effect), and recently some workers published the idea that to evaluate the hearing loss due to the acoustic trauma and other etiologies in older pers- ons, this physiological loss must be subtracted from his audiometric loss of hearing. Considering this view hearing acuity was measured on 412 subjects without any subjective difficulty of hearing andny pathological changes of the ear. Subjects were divided into 15 groups of every five year, and the results were statistically discussed.
The main results obtained were as follows :
1) On the whole, the hearing acuity decreased gradually with the increase of age. This phenomenon was not noticeable until about 50 years old, but became more distinct over this age.
2) Individual difference of the hearing loss also became larger with the increase of age, especially in groups over 50 years old. Statistical significance calculated by variance ratio was found between the individual differences of nearly all groups over 50 years and that of younger groups.
3) Hearing acuity was impaired mainly in the high frequency region, and the gradual sloping form was predominantly found in the audiogram.
Nearly all subjects showed the bilateral symmetrical audiogram in both ears. Femalle group showed a little less loss than the male group.
From the results mentioned above, following conclusions were drawn.
The changes of the hearing acuity by age manifest itself not only as the increase of the hearing loss but also as the increase of the individual difference among subjects in the same age group. So, in order to evaluate and define the physiological hearing loss by age, it is not fully adequate to take an account of only its mean value of the hearing loss.