路透社纽约健康消息 7月份出版的《儿科学》杂志上一项研究指出，大量美国少年儿童的听力下降可能在学龄期听力筛选检查时被漏掉。研究发现，超过12%的儿童存在噪音性听力下降。噪音性听力下降是指听域变化时听不清楚，给日常生活带来不便，如噪音背景中的对话有困难。估计全美有500多万少年儿童受噪音性听力下降影响。
根据1988年到1994年间以家访和听力测试的形式对5,200多名6至19岁美国少年儿童进行的调查资料，美国联邦疾病控制和预防中心研究人员分析发现，有噪音性听力下降的小孩多数为轻度听觉损害，只有5%有中度到高度损害。噪音性听力下降在12至19岁的青少年中最普遍，大约有16%受其影响。儿童则约有9%有某种听力受损。总之，大部份参加研究的儿童都有不同程度的听力下降，由于症状不典型，没有被筛选检查出来。
这些结果表明，常暴露于噪音中的少年儿童，听力容易受损。飞机、轻武器、电动工具、立体声，甚至玩具都会损害听力，但研究人员不能确定孩子噪音性听力下降的噪音来源。
研究人员目前也还不知道这种儿童的噪音性听力下降是暂时性的还是永久性的。研究人员指出，成年人持续暴露于过多的噪音中会使噪音性听力下降恶化，但是，当离开噪音数分钟或几星期后，听力可以从暂时性噪音性听力下降中恢复。研究人员指出，噪音性听力下降是可以预防的，因此，首先应该保护孩子免受噪音对听力造成的损害。
来源：《儿科学》2001;108:40-43
Many U.S. Kids May Have Noise-Related Hearing Loss
NEW YORK (Reuters Health) - A substantial number of American children and teens may be sustaining hearing damage that school-age screening might not pick up, according to a national study of more than 5,200 6- to 19-year-olds.
Researchers found that more than 12% of the children had hearing damage known as noise-induced hearing threshold shifts, or NITS. The condition refers to a change in the threshold beyond which a person cannot hear clearly. In everyday life, it can amount to problems such as having trouble hearing normal conversation amid background noise.
The current findings, published in the July issue of Pediatrics, suggest that more than 5 million American children and teens may be affected by NITS in one or both ears.
In addition, most of the affected children in the study had hearing damage in a frequency range not typically tested in school-age children, report researchers led by Amanda Sue Niskar of the Centers for Disease Control and Prevention (news - web sites) in Atlanta, Georgia.
The study was based on household interviews and hearing tests conducted between 1988 and 1994. Niskar‘s team found that of the children with NITS, the majority had only slight hearing damage, while 5% had ``moderate to profound‘‘ damage. NITS was more common among teens, with nearly 16% of 12- to 19-year-olds affected. Close to 9% of younger children showed some hearing damage.
``These results,‘‘ Niskar and her colleagues write, ``suggest that children are being exposed to hazardous levels of noise, and children‘s hearing levels are vulnerable to these exposures.‘‘
While the researchers could not determine the sources of NITS among these children, they note that airplanes, firearms, power tools, stereos and even toys have decibel levels that can damage hearing.
Also unknown is whether these hearing problems were temporary or permanent. Continued exposure to excessive noise can make NITS progressively worsen, Niskar and her colleagues point out. On the other hand, adults have been shown to recover from temporary NITS within minutes or weeks of getting away from the auditory assault.
``The resiliency of a child‘s auditory system with respect to noise exposure is unknown and should be a topic of additional investigation,‘‘ the authors write.
But since NITS is preventable, they conclude that protecting children from hearing damage in the first place should be a priority.
SOURCE: Pediatrics 2001;108:40-43.
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