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Why is autism so prevalent in highly developed countries?

Posted on Mar 09 , 2012 in Blog

A friend of mine recently said ““What really makes me crazy about autism is that I don’t remember any kid having it when I grew up nor do I see it when I travel and spend time in South America. Why then is it so prevalent in highly developed countries?”

Assuming they get questions like this often, I contacted our local Autism Speaks office in St. Louis and they supplied me with this long but detailed answer. Please read below.

FROM AUTISM SPEAKS:
This question leads the way in our research and is the reason for an ever growing need to fund that research.

In the last two decades, autism prevalence as report in the scientific literature has increased by more than 600%. In 2009, the latest estimate of autism prevalence in the United States, as report by the Centers for Disease Control was 1 in 110 children. Since then, a number of studies have sought to investigate the cause(s) of this dramatic increase in autism prevalence over time. Studies suggest that at least a portion of the increase in prevalence can be attributed to changes in diagnostic practices and increased awareness of autism over time, as well as other social factors such as advanced parental age. However, converging evidence also suggests that while these factors account for a portion of the increase, they cannot alone explain the dramatic rise in autism prevalence.

• The criteria for assessing autism has changed over the last 20 years resulting in a broadening of autism diagnoses and the identification of cases that would not have been diagnosed as such using older criteria. Looking at a population of children researchers reported that approximately 26% of the rise in autism could be directly attributed to changes in diagnostic criteria, specifically the shift from mental retardation diagnoses to autism diagnoses.

• Another aspect of the autism landscape that has changed over the past 20 years is an increase in the awareness of autism among the general public as well as healthcare professionals. Investigators found that children living in close proximity to another child that had been previously diagnosed with autism had a better chance of being diagnosed with autism themselves. The proposed explanation is information diffusion, or parents talking to and educating other parents about autism resulting in an increased likelihood of their children being diagnosed. It is estimated that 16% of the increase in autism prevalence over time was due to social influence and increased awareness.

• An additional social factor that has been implicated in contributing to the increase in autism prevalence is advanced parental age. A number of recent publications investigating the relationship between parental age and autism have demonstrated that older parents are at increased risk for having a child with autism. This is not surprising since increased parental age is associated with a slightly increased risk for other developmental disorders as well. Researchers reported that the increase in parental age over time can account for 11% of the increase in prevalence over the same time period.

Based on the abovementioned research, approximately 53% percent of the increase in autism prevalence over time may be explained by changes in diagnosis (26%), greater awareness (16%), and an increase in parental age (11%). While this research is beginning to help us understand the increase in autism prevalence, half of the increase is still unexplained and not due to better diagnosis, greater awareness, and social factors alone. Environmental factors, and their interactions with genetic susceptibilities, are likely contributors to increase in prevalence and are the subject of numerous research projects currently supported by Autism Speaks.

The prevalence of autism worldwide is not known because screening and treatment for young children with developmental disabilities in developing countries is often inconsistent or altogether absent. From the information that is available it is clear that autism is a massive challenge facing families worldwide. The latest epidemiological estimates report that there are 1.7 million individuals in India with autism. There are 1.8 million reported cases of autism in China. It is likely that the number of children and families impacted by autism in Africa, South America and Asia numbers additional millions. Most of these families lack the guidance, support and understanding that would allow them to help their child reach his or her potential.

The increase in autism prevalence is real and the public health crisis is growing. More families are affected by autism today than ever before. While Autism Speaks has cast a wide net to explore the role of genetic and environmental factors in increasing the risk for autism, the research community requires additional funding support to increase the pace of discovery. Never before has the need for research into the causes of autism and effective treatments for autism been greater.

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