1 January 2003
of Autism Growing, Study Finds
By Sandra Blakeslee
is about 10 times more prevalent today than it was in the 1980's,
according to the largest United States study ever on the problem.
Some of the increase can be explained by widened definitions of
the disorder, the researchers said, but the explanation for the
rest of the increase is unknown.
study, conducted in metropolitan Atlanta in 1996, found that
3.4 in every 1,000 children between the ages of 3 and 10 had diagnoses
of mild to severe autism during that year. In the late 1980's, 4
to 5 out of every 10,000 children were thought to be afflicted.
higher prevalence rate, described in today's issue of the Journal
of the American Medical Association, is in line with rates found
in recent but smaller studies here and abroad in which the prevalence
rate of autism is 4 to 6 out of every 1,000 children.
researchers, from the federal Centers for Disease Control and Prevention,
said the prevalence rates they found would mean that at least 425,000
American children under age 18 have some form of autism, including
114,000 children under age 5.
Marshalyn Yeargin-Allsop, an epidemiologist at the National Center
on Birth Defects and Developmental Disabilities, led the new study
which was carried out in the federal agency's backyard of metropolitan
of the increased prevalence can be explained by changes in the definition
of autism, a brain disorder in which normal social interaction is
difficult or impossible. In recent years, the definition has been
widened to include milder forms of the disorder.
experts believe autism results from an interplay of genes and unknown
environmental factors. "No strong candidate environmental exposures
have been identified," said Dr. Eric Fombonne, an autism expert
at McGill University and the Montreal Children's Hospital in Quebec.
"Claims of an association with measles-mumps-rubella immunization
have not been borne out by recent studies, and evidence for causal
association with other exposures, such as mercury containing vaccines,
Iversen, the mother of an autistic child and the co-founder of Cure
Autism Now, an advocacy group in Los Angeles, said the findings
reported today were not surprising. "We are in the midst of
an autism epidemic in this country," she said. We need the
government to step in and take emergency action."
Yeargin-Allsop said the researchers canvassed schools, clinics,
physicians, non-profit programs and other places autistic children
might go for services in 1996. Studies that look at autistic children
in just one setting, such as special clinics, tend to find lower
prevalence rates, she said.
reviewed the medical records of each child and determined if autism
was diagnosed accurately. They did not examine the children in person.
Out of the 289,456 children between the ages of 3 and 10 years living
in the five counties of metropolitan Atlanta in 1996, 987 had mild
to severe autism, giving a prevalence rate of 3.4 per thousand.
Yeargin-Allsop said 18 percent of the children found to have autism
in 1996 had never been diagnosed accurately. Many were classified
as having general developmental difficulties whereas higher functioning
children were missed entirely.
Atlanta study found that prevalence rates were the same for black
and white children, but confirmed earlier studies that autism is
four times more common in boys than in girls.
Yeargin-Allsop said the federal agency is conducting similar surveillance
studies across several states to provide a more complete picture