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May 4, 2006 -- At least 300,000 school-aged U.S. children had ever been diagnosed with autismautism as of 2003-2004, the CDC estimates.
That estimate is based on two national health surveys conducted by the CDC in 2003-2004. The results appear in the CDC's Morbidity and Mortality Weekly Report.
The surveys asked parents if their child had ever been diagnosed with autism. The surveys show that about 5.6 per 1,000 children aged 4-17 years had a parent-reported autism diagnosis.
The surveys also show that kids with parent-reported diagnosed autism were more likely than other children to have special health care needs and "high" levels of emotional symptoms, conduct problems, hyperactivity, and peer problems.
The CDC describes autism and related conditions as "lifelong developmental disabilities characterized by repetitive behaviors and social and communication problems."
'Major Public Health Concern'
"Taken together, all these studies affirm that autism is a condition of major public health concern that affects many families," Jose Cordero, MD, MPH, told reporters in a teleconference.
Cordero directs the CDC's National Center on Birth Defects and Developmental Disabilities (NCBDDD).
Cordero says the prevalence rates are within the range of previous estimates. "The surveys reported today by themselves can't tell us much about autism's trends," Cordero says.
"We recognize that parents want answers," Cordero says. "They want to know how to protect their children; what can they do to help them stay healthy. If children have autism, parents want to know what caused it, the most effective treatments, and how can they lower their risk if they plan to have other children.
"This is perfectly understandable," Cordero says. "We share the frustration about not having more answers about the causes and cure of autism."
About the Surveys
The CDC's latest numbers came from the CDC's National Health Interview Survey (NHIS) and the National Survey of Children's Health (NSCH).
Participants were parents, but the same parents didn't take both surveys. The surveys covered various health topics.
One question on both surveys asked, "Has a doctor or health care provider ever told you that [child's name] has autism?" The NHIS estimates that 5.7 per 1,000 kids had a parent-reported autism diagnosis. The NSCH had a similar estimate of 5.5 per 1,000 kids.
The NSCH also showed that nearly 94% of kids with a parent-reported autism diagnosis had special health care needs, compared with almost 20% of other kids.
Those health care needs included prescription medicines; treatment or counseling for emotional, developmental, and behavioral problems; special therapy such as physical, occupational, or speech therapy; limits in the child's ability to do things done by most children of the same age; and greater need or use of medical, mental healthmental health, or educational services than usual for most other children of the same age.
Other Autism Findings
The surveys also showed three other patterns:
Autism diagnoses may be delayed in some children, but since the age-related findings might have been due to chance, those results should be interpreted "cautiously," CDC epidemiologist Laura Schieve, PhD, told reporters, in the conference call.
The findings about Hispanic children "might partially reflect differences in symptom recognition, diagnosis, and/or access to services," Schieve says.
Previous Estimates
Two previous CDC studies in selected U.S. locations estimated the prevalence of autism-spectrum disorders (ASD). One of those studies showed ASD prevalence as 3.4 per 1,000 children. The other study showed ASD prevalence of 6.7 per 1,000 children.
However, the latest studies -- the 2003-2004 NHIS and NSCH -- only asked about autism diagnoses. They didn't mention autism-spectrum disorder, ASD, or any other terms from the autism spectrum.
"That's a limitation," CDC epidemiologist Laura Schieve, PhD, told reporters, in the conference call.
"We do not have data to know how parents who have a child who was diagnosed with Asperger disorder, for example, might have responded to the autism question," Schieve says. Asperger disorder is part of the autism spectrum.
"It is possible that they understand that to be autism-spectrum disorder and therefore had responded affirmatively to this question. We cannot rule out that possibility," Schieve says. "But it is one of the limits of both of these surveys that those specific data were not collected for us to disentangle that."
The new numbers only reflect diagnosed autism cases reported by parents. Children's medical records weren't checked, and some children may have undiagnosed autism.
"The major challenge we have right now is early recognition, and I think that these data do point out that we have a major problem with that, and that's why it's so important to educate both pediatricians and ... parents about the early signs of autism," Cordero says.
SOURCES: Jose Cordero, MD, MPH, director, National Center on Birth Defects and Developmental Disabilities, CDC. Morbidity and Mortality Weekly Report; May 5, 2006; vol 55: pp 481-486. CDC: "Fact Sheet: CDC Autism Research." Laura Schieve, PhD, epidemiologist, National Center on Birth Defects and Developmental Disabilities, CDC. CDC: "How Common Are Autism Spectrum Disorders (ASD)?" News release, CDC.