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ANATOMY, PHYSIOLOGY, AND DISORDERS OF THE AUDITORY SYSTEM - PART 8

Kết quả cho thấy tần số mất thính lực cao làm tăng tuổi (Hình 9,10). Các dữ liệu trong hình. 9,10 hiển thị mức trung bình của tám nghiên cứu được công bố bao gồm dữ liệu từ hơn 7.600 nam giới (Hình 9.10A) và gần 6.000 phụ nữ (Hình 9.10B) (310). Những nghiên cứu này hiếm khi xác định các tiêu chí đã được sử dụng | Chapter 9 Hearing Impairment 217 FIGURE 9.10 A Average hearing loss in different age groups of men. Results from eight different published studies based on a total of 7 617 ears. B Average hearing loss in different age groups of women. Results from eight different published studies based on 5 990 ears reprinted from Spoor 1967 . The results show that the high frequency hearing loss increases with age Fig. 9.10 . The data in Fig. 9.10 show the averages of eight published studies comprising data from more than 7 600 men Fig. 9.10A and almost 6 000 women Fig 9.10B 310 . Such studies rarely define which criteria were used for inclusion in the studies and it is therefore possible that the results may reflect hearing loss that is caused by factors other than age. In large population studies such as those compiled by Spoor 310 many individuals have been exposed to noise which results in greater hearing loss at 4 kHz than other frequencies see p. 219 . A cross-sectional and longitudinal population study of hearing loss and speech discrimination scores in an unselected population of individuals aged 70 Fig. 9.11 228 showed that both these groups of individuals had high speech discrimination scores Fig. 9.12 somewhat lower in men than women. Exposure to noise affected hearing in men more than in women and that appears as a slightly greater hearing loss for high frequencies. The reason for this gender difference may be that many men had noise induced hearing loss but there may be other reasons related to hormonal influence on the progression of age-related changes in the cochlea and possibly differences in the age-related change in neural processing of sounds. M.B. Moller 228 also provided the distributions of hearing loss among the individuals of the study Fig. 9.11 and these data show that the hearing loss in the men and women studied is far from being normally Gaussian distributed. For low frequencies the distributions are skewed with a long tail towards larger hearing .