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Teens show rise
in hearing loss
By Nathan Seppa
The prevalence of hearing loss in teenagers rose by nearly one-third in recent
years compared with the rate in the
late 1980s and early 1990s, a new study
shows. The findings come as a surprise
to the study’s authors, who had expected
overall hearing to improve thanks to publicity about the risks of exposure to loud
music and the advent of childhood vaccines against meningitis and pneumonia
that can prevent many ear infections.
But in the Aug. 18 Journal of the American Medical Association, the scientists
report that the portion of U.S. adolescents aged 12 to 19 with any hearing loss
rose from 14.9 percent during the 1988
to 1994 period to 19. 5 percent in 2005
and 2006.
Researchers based the analysis on
information gathered from nearly 3,000
kids in the earlier time frame and more
than 1,700 in the later sampling. The
findings suggest that as many as 6. 5 million teens in the United States now have
some hearing loss.
The surveys used largely similar questionnaires and standard hearing tests in
which “any hearing loss” was defined as a
loss of 15 decibels in at least one ear. That
is, a person was determined to have some
hearing loss if a tone had to be increased
by 15 dB or more beyond the standard
detection level to be heard at least half
the time.
Hearing loss of 25 dB or greater is less
common, particularly in children. But it
also rose, from 3. 5 to 5. 3 percent, between
the study time frames. The rate of hearing
loss increased in high — but not low — frequencies, the researchers found.
This study wasn’t designed to find
the cause of hearing loss, says study
coauthor Sharon Curhan, a physician
and researcher at Harvard Medical School
and Brigham and Women’s Hospital in
Prevalence of hearing loss among
U.S. children ages 12–19
25 Any loss
20
Any high
frequency
loss
1988 –
1994
2005 –
2006
Percent
10
15
5
Any
bilateral
loss
source: shargorodsky et al/JaMa 2010
The percentage of U.S. adolescents with
measurable hearing loss rose by almost a
third in just over a decade, a study finds.
0
Boston. While noise exposure is a known
culprit, diet, medical care, lack of exercise
and obesity might also play a role, she says.
When asked about their exposure to
loud music, kids with good hearing didn’t
give answers substantially different from
those offered by kids with poorer hearing. But that may not tell the whole story.
“People underestimate their noise
exposure,” Curhan says. A single brief
noise can compromise hearing levels.
Gene activity may predict TB fate
information could reveal who will go from infection to disease
By Tina Hesman Saey
Thanks to molecular profiling, scientists
now have a better idea about how a mass
killer selects its victims.
Mycobacterium tuberculosis infects
one-third of people worldwide. But only
about 10 percent of people infected will
actually get sick with the debilitating
lung disease tuberculosis. Scientists currently have no way to predict who those
people are.
Now, a consortium of researchers
has compiled profiles of gene activity
in the blood of people with dormant
TB infections, people with active infec-
tions and healthy people. Such profiles
may help predict who will succumb
to TB, the researchers report in the
Aug. 19 Nature.
