- Young people who turn up their personal
stereos too loud risk hearing loss, researchers have found.
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- The investigators assessed hearing status
in 1208 young men aged 18-24 years who were having medical examinations
at selection centres for the army in France.
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- Writing in the medical journal The Lancet,
the researchers, led by Dr Agnes Job, from the Centre de Recherche du Service
de Sante de Armees at La Tonche, Cedex, said that the use of personal stereos
for at least one hour a day was found to damage the youngsters' hearing.
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- Approximately one in five of those youngsters
who used personal stereos with the volume turned up high experienced problems
with their hearing.
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- The level of noise at which they could
detect a sound was much higher than those with normal hearing. The phenomenon
was found for sounds at all frequencies tested between 0.5kilohertz and
8.0kilohertz - the normal human hearing frequency range.
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- The harmful effect, however, was strongly
dependent on whether the men had suffered repeated middle-ear infections
in infancy or in childhood.
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- Personal stereos had no effect on men
without a history of ear infections. For those who had suffered childhood
ear infections the loudness threshold at which they could hear sounds was
on average 11 decibels higher than normal.
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- Personal stereos also increased the risk
of ringing in the ears in these individuals.
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- Previous studies have shown harmful effects
of personal stereo use on hearing performance in young adults. But the
effects were very limited.
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- "We show that personal stereo use
has clinically important effects in men with repeated episodes of otitis
media in childhood," the researchers write.
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- "Our results shows the importance
of curing otitis in childhood and of a prevention policy.
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- "Young people with a history of
repeated episodes of otitis media should be warned that personal stereo
use is a risk factor for deafness."
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- The research also found that as many
as 38% of those examined who attended loud concerts and discos twice a
month or more suffered damage to their ability to pick up lower frequency
sounds.
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- Hearing thresholds at higher frequencies,
2 kilohertz and 4 kilohertz, were significantly increased in 18% of men
who had spent at least six months in noisy occupations.
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