Henderson D, Saunders S S
Department of Communicative Disorders and Sciences, State University of New York at Buffalo, 14214, USA.
Ear Hear. 1998 Apr;19(2):120-30. doi: 10.1097/00003446-199804000-00004.
The rate of growth of hearing loss was examined in a population of workers exposed to noise. Of special interest was the course of loss in the first 10 yr of work, for which international standards provide little information. Based on the International Standards Organization (ISO) 1999 compilation, it was hypothesized that the proportional growth of hearing loss would be constant in log years.
Of 5000 workers compensated for hearing loss by a railroad, 500 were selected at random for analysis. For these workers, 2660 audiograms were available. The audiograms were distributed unsystematically over work careers, and for most workers were sparsely distributed. Thresholds were age corrected using ISO 1999 Annex B and averaged as a function of years on the job for two partitions, 0.5, 1, 2, and 3 kHz and 2 and 4 kHz. The average curves were compared with projections based on the ISO 1999 data as suggested by Dobie (1993a). A subset of workers with substantial hearing loss when hired was examined to evaluate the effect of pre-existing hearing loss.
Hearing was worse at hire for this sample of workers than suggested by ISO 1999 Annex B for an unscreened sample of the general population at comparable ages. As a result, the early hearing loss was underpredicted by the ISO 1999 projection. Except at the earliest years of employment, the rate of growth toward the final hearing loss for the mean of the sample of workers was approximated by the projection from ISO 1999. The ISO 1999 projection is based on growth of the percentage of loss at the final audiogram obtained each year. In subgroups of workers, i.e., for the lower quartile and for the upper quartile of the sample, the projection based on ISO 1999 was similarly effective. Workers hired with prior loss showed growth of hearing loss that was flatter than that of either the mean of all workers or the ISO 1999 projection, but the growth curve for these workers approximated the average curve shifted to later years to bring the initial loss into correspondence with the predicted loss.
For a group of workers exposed to a noisy environment, growth of hearing loss can be projected fairly well based on ISO 1999, without knowledge of the details of spectrum or level of noise exposure. This suggests that it would be possible to allocate the percentage of a known total hearing loss acquired in a group of workers on a year-by-year basis, given knowledge of work history for a claimant population in the absence of detailed knowledge of the exposure or detailed sequential audiometric data.
研究噪声暴露工人人群中听力损失的增长速率。特别关注工作头10年的听力损失进程，而国际标准对此提供的信息很少。基于国际标准化组织（ISO）1999年的汇编资料，推测听力损失的比例增长在对数年份中是恒定的。
在5000名因听力损失获得铁路公司赔偿的工人中，随机选取500名进行分析。这些工人有2660份听力图。听力图在整个工作生涯中分布无规律，且大多数工人的听力图分布稀疏。使用ISO 1999附录B对阈值进行年龄校正，并针对0.5、1、2和3千赫以及2和4千赫这两个频段，将其作为工作年限的函数进行平均。将平均曲线与多比（1993a）建议的基于ISO 1999数据的预测进行比较。对一组入职时就有明显听力损失的工人进行了研究，以评估既往听力损失的影响。
与ISO 1999附录B针对可比年龄的未筛查普通人群样本所建议的情况相比，该组工人入职时听力更差。因此，ISO 1999的预测低估了早期听力损失。除了就业的最初几年外，该组工人样本均值向最终听力损失的增长速率与ISO 1999的预测相近。ISO 1999的预测基于每年获得的最终听力图上损失百分比的增长情况。在工人亚组中，即样本的下四分位数组和上四分位数组，基于ISO 1999的预测同样有效。入职时就有听力损失的工人听力损失的增长比所有工人的均值或ISO 1999的预测更为平缓，但其增长曲线近似于平均曲线，但向后推移，以使初始损失与预测损失相符。
对于一组暴露于噪声环境的工人，在不了解噪声频谱或暴露水平细节的情况下，基于ISO 1999可以较好地预测听力损失的增长情况。这表明，在缺乏暴露细节或详细的连续听力测试数据的情况下，若已知索赔人群的工作史，就有可能逐年分配一组工人中已知的总听力损失的百分比。
