May 3, 2011
Study Questions ‘Austism Epidemic’ In The UK
Despite past studies claiming a rise in adults with autism spectrum disorder (ASD), a recent UK study has found no traces of an "autism epidemic."
The prevalence of adults with ASD in England was estimated to be 9.8 per 1,000 population, according to a May report in the Archives of General Psychiatry.Recent surveys conducted among adults and children in England have shown an ASD prevalence of about 10 in 1,000, which is somewhat higher than some earlier studies that have estimated prevalence of 4.4 per 10,000 population and 12.7 per 10,000 population.
"It is not known whether this reported increased prevalence reflects case finding changes or increasing incidence due to newly emerging causes," authors of the study stated as context.
The authors noted a lack of validated information about the rate of ASDs in British adults, possibly because symptoms may not be obvious in some.
"Adults with ASDs are more likely to be recognized and supported if they also have severe intellectual disability; those with higher levels of functioning tend to be overlooked in the community," said the authors.
Researchers in the study found nearly one percent of Britons older than 16 years have autism, a rate similar to that seen in children. Younger people were no more likely to be affected than older ones, however, which would have been expected if the condition were truly on the increase.
"It was surprising to all of us," said Dr. Traolach Brugha, a psychiatrist at the University of Leicester, who worked on the study. "If this study is correct, it does put a big question mark over the autism epidemic."
The new survey is the first to give an estimate of autism rates among adults in the general community.
ASD ranges in severity from mild Asperger's Syndrome to severe mental retardation and social disability. ASD affects nearly one percent (one in 110) children in the United States, according to estimates from the Centers for Disease Control and Prevention (CDC).
The CDC estimated in 2009 that ASD rates had gone up dramatically in the US since 2002. Older studies from the UK also suggested rates of autism had increased in recent years.
The previous research into England's population of adults with ASDs has been based mostly on self-reported data, which could affect the results.
Brugha and colleagues from other English colleges and the National Center for Social Research devised a multipart study. The first phase involved a sample of 13,171 households from the 2007 Adult Psychiatric Morbidity Survey in England, of which 57 percent the households selected, responded.
Researchers used the Autism-Spectrum Quotient self-questionnaire and other measures to select 618 individuals who were interviewed using the Autism Diagnostic Observation Schedule, Module 4 (ADOS-4), and also provided additional information about other factors such as age, sex, marital status, housing status, income, education, employment, and use of government benefits. None of the study participants had previously received an evaluation for or diagnosis of autism.
Using an upper-limit of ten or greater on the ADOS-4 to indicate possible ASD, the authors determined that the overall prevalence of ASD in the English population was estimated at 9.8 per 1,000. The rate of ASD for men was 18.2 per 1,000, and 2.0 per 1,000 for women.
Despite the findings, only 19 individuals out of 2,828 in the study met the criteria for ASD corresponding to the 9.8 per 1,000 adults.
The researchers noted that the adult prevalence of ASD they found is similar to the prevalence in children, but also suggest that their findings need to be independently replicated.
Fears that the condition is becoming more common in children, researchers and parents have sought fiercely for underlying reasons. So far those efforts have not paid off. And the much-reported claim that childhood vaccines could be the culprit has been widely discredited.
More and more research suggests that some if not all of the increase in autism may be due to changes in how, and how often, the disorder is diagnosed. Children who have been classified as mentally retarded or merely eccentric, for instance, may not be labeled with ASD instead.
"That simply means more people are coming forth and being recognized," Brugha told Reuters Health.
Brugha said he was confident in the results of the study, but other studies are needed to confirm this given the small number of people in the study were found to have autism.
He was disappointed to discover that none of those who got the diagnosis based on the study's clinical assessment were aware of their condition. "None of them had been diagnosed (previously) with autism," said Brugha. "I think for me the issue is that people have been ignoring autism in adulthood and only focusing on children."
On the Net: