[EDLING:175] Signing 'increases deafness rates'

[Shannon Sauro]

This article is from the BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/3665939.stm

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Signing 'increases deafness rates'

Sign language may be behind rising rates of inherited deafness, according to
researchers.

The proportion of people who are born with profound hearing loss has doubled
over the past 200 years.

Researchers at Virginia Commonwealth University in the United States have
traced the increase back to the introduction of sign language in the early
1800s.

They say the introduction of sign language allowed people who are deaf to
communicate with each other more easily.

They say it also led to many more people with hearing loss marrying.

At least 85% of individuals with profound deafness marry another deaf person
Professor Walter Nance

The researchers believe the decision of so many people with inherited hearing
loss to marry has been behind the increase in deafness rates.

Gene mutations
More than 100 genes are involved in hearing loss. As a result, most people who
are deaf have children with normal hearing because they pass on different
genes.

However, a mutation in one gene, the connexin gene, is responsible for 50% of
inherited deafness.

If both parents have this mutation, they will pass it on to their children,
who will usually be born deaf.

The researchers used computer modelling to show what effect intermarriage
between people with inherited deafness has over many generations.

They found that intermarriage between people who are deaf can lead to a
significant increase in the number of people with inherited hearing loss.

This is largely because they have children with the condition who themselves
go on to marry other people with this type of genetic deafness.

"In the United States, at least 85% of individuals with profound deafness
marry another deaf person," said Professor Walter Nance, who led the study.

"In the case of marriages among couples who both have the same form of
recessive deafness, all their children will be deaf and capable themselves of
also passing on the altered gene to their offspring.

"In addition, as many as 3.5% of the hearing population in the United States
may carry single mutations involving the connexin 26 complex, making this one
of the most commonly recognized single gene defects."

Professor Nance said areas in the United States with a history of schools that
teach through sign language have increased rates of genetic deafness.

"In regions where national or state-wide schools for the deaf have been
established and marriages among students have occurred, we've seen an
amplification of the commonest form of recessive deafness in the overall
population."

Professor Nance believes the findings may explain how speech evolved in
humans.

"When you think about how the onset of selective marriages among deaf
populations led to an increase in specific mutations for deafness, you easily
can see how these same forces might have contributed to the spread of genes
for speech among Homo sapiens 160,000 years ago," he said.

"If you were one of the first primates with an ability to communicate by
speaking, wouldn't you want to select a partner who could whisper sweet
nothings in your ear?"

Brian Lamb, director of communications at the RNID, said: "This research
provides an interesting insight into why a specific genetic form of deafness
has become more common.

"It is not surprising that people with a shared culture of deafness marry. And
if both people have the same specific genetic cause of deafness, this will be
passed down the generations.

"RNID supports the rights of deaf people to marry one another. As well as
looking at the genetic causes of deafness it is also important for society to
develop ways to improve communication for deaf people so that they live active
and fulfilled lives integrated in society."

The findings will be published in the American Journal of Human Genetics in
June.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/3665939.stm

Published: 2004/04/28 15:31:33 GMT

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