Posts Tagged ‘prevalence’

Commentary on the LA Times Series on Autism

January 3, 2012 18 comments

Posted by Autism Speaks scientific advisory board member Irva Hertz-Picciotto, PhD, MPH. As an epidemiologist at the University of California-Davis MIND Institute, Hertz-Picciotto studies exposures to environmental chemicals, their interactions with nutrition and pregnancy and their effects on prenatal and early child development.

Alan Zarembo’s series on autism in the LA Times  covers a great deal of territory and has brought to light a wide range of personal stories that exemplify the complexity of issues surrounding autism diagnosis, treatment choices and effectiveness, impact on families and population incidence. Zarembo should be commended for the substantial work he has done researching inequities in the delivery of services. Of notable concern, he has put a spotlight on what appear to be serious racial and ethnic disparities in the California Department of Developmental Services (DDS) system and the provision of therapies. If his figures are correct, this result should stimulate an analysis of how to right this situation and ensure that appropriate opportunities are made available to all families with affected children.

Zarembo has also highlighted adults living with an autism spectrum disorder (ASD) but diagnosed late in life. We have too long overlooked the struggles faced by adults with autism as they try to find ways to be productive, live independently and connect with others.

My remaining comments pertain to Zarembo’s conclusions about the rise in autism diagnoses and the role of environmental factors. First, he is right that there is substantial variability in rates of diagnoses in different regions, and that we should not confuse diagnoses with the actual incidence of disease. Not all persons who meet criteria have been correctly diagnosed, and the degree to which this is true has likely changed over time.

Nevertheless, impressions are not the same as a scientific analysis. Zarembo has not demonstrated that the rise is purely social and cultural.  My colleague Lora Delwiche and I published the first quantitative analysis of how much of the increase in diagnosed cases in California could be explained by artifacts (changes in diagnostic criteria, earlier age at diagnosis and inclusion of milder cases).1 We used California state data that provided statistics over many years and found that the numbers simply do not add up. In other words, the actual increase has been far larger than these artifacts could have produced. Combining our results with those of another research team, it appears that about half of the increase in diagnoses in California is due to changes in diagnostic criteria or practices.2 These results left about a three-fold increase unexplained as of 2007. And autism diagnoses in California have continued to rise both in areas with low rates and in areas with high rates. Zarembo is interested in explaining the geographic variation, but the explanations for variation spatially are not necessarily the explanations for variation over time.

These statements were particularly misleading:

“No study points to an environmental reason for the worldwide explosion in cases over the last two decades.

Given the slow pace of genetic change in large populations, genes can’t account for the surge either.

That suggests the explanation for the boom lies mainly in social and cultural forces, notably a broader concept of autism and greater vigilance in looking for it.”

The logic that leads from the first two sentences to the third involves huge assumptions.

How many studies have been done of environmental causes? Very few!  And of these, most were extremely poor studies involving very small samples or lacking individual-level data. Is it surprising we’ve uncovered few leads?  The funding for environmental factors has been paltry – somewhere around $40 to $60 million over the last 10 years, while more than $1 billion has been spent on studying autism genetics.  To imply that environmental factors can be dismissed and that only social/cultural factors should be pursued is nonsensical.

It should be noted, however, that if anyone is looking for “one” environmental factor to explain the increase, they will certainly be disappointed. It doesn’t exist. Autism is far too complex. Moreover, to the extent the increase is due to diagnostic differences over time, we need to find explanations both for the increasing numbers of diagnoses and for the autism that has been around “all along.” In fact, data are emerging about quite a number of environmental factors. In 2011, major papers were published supporting contributions from maternal nutrition around the time of conception (here and here), traffic-related air pollution, and season of conception.3-6 Earlier papers indicated associations with pesticides  (here and here) and air pollution.7-9

One concern raised about the increase in diagnoses is a type of ‘inflation’ from inclusion of a growing number of high-functioning persons whose diagnosis is more likely to be Asperger syndrome than classic autism. This may apply to some studies of changes over time, but in our analysis of CHARGE study data, most of the cases were low functioning.10 This would likely be true for the majority of persons with ASD served by the California Department of Developmental Services (DDS), because in order to qualify for state services, they must have “significant functional limitations” in three areas of major life activities. This requirement would exclude most of those who are higher functioning.

With regard to genetics, Zarembo’s article leaves out the most current information: the largest and most statistically robust study of twin pairs found that 38 percent of concordance is due to shared genetics with 58 percent due to shared environmental factors (most likely prenatal and perinatal).11 This result completely overturns the widespread assumption, based on a number of previous small studies, that the causes of autism are overwhelmingly heritable, or genetic. Unfortunately, most analyses of twins make the incorrect assumption that genes and environment do not interact to influence risk for disordered brain development. This interaction is real, and one study has already shown a whole class of genes that primarily affect development in children whose mothers had not taken prenatal vitamin supplements during the months preceding and immediately following conception. 3

In summary, Zarembo’s investigative journalism provides unusual depth into difficult aspects of autism occurrence and the social policies that bear on the lives of affected families. He has raised several critical challenges facing the autism community. What was lacking from his series is a more balanced view of the role environment likely plays and the need to advance the agenda of discovering modifiable causative factors.

Autism Speaks is one of a few organizations that have begun to turn in this direction. I look forward to a continued strong commitment by Autism Speaks and others willing to support and significantly expand the scientific research aimed at identifying and understanding environmental contributions to autism, factors driving increased prevalence and ways to intervene so as to eliminate or lower human exposure levels. This will be the fastest road to reducing the occurrence of ASD in the next generation.

1             Hertz-Picciotto I, Delwiche L. The rise in autism and the role of age at diagnosis. Epidemiology 2009;20: 84-90.
2             King M, Bearman P. Diagnostic change and the increased prevalence of autism. Int J Epidemiol. 2009; 38:1224-34.
3             Schmidt, R J, et al. Prenatal vitamins, one-carbon metabolism gene variants, and risk for autism. Epidemiology 2011;22:476-85.
4             Cheslack-Postava K, Liu K, Bearman PS. Closely spaced pregnancies are associated with increased odds of autism in California sibling births. Pediatrics 2011;127:246-53.
5             Volk HE, Hertz-Picciotto I, Delwiche L, Lurmann F, McConnell R. Residential proximity to freeways and autism in the CHARGE study. Environ Health Perspect 2011;119: 873-7.
6             Zerbo O, Iosif AM, Delwiche L, Walker C, Hertz-Picciotto I. Month of conception and risk of autism. Epidemiology 2011;22:469-75.
7             Roberts EM, et al. Maternal residence near agricultural pesticide applications and autism spectrum disorders among children in the California Central Valley. Environ Health Perspect. 2007;115:1482-9.
8             Eskenazi B, et al. Organophosphate pesticide exposure and neurodevelopment in young Mexican-American children. Environ Health Perspect 2007;115:792-8.
9             Windham G, Zhang L, Gunier R, Croen L, Grether J. Autism spectrum disorders in relation to distribution of hazardous air pollutants in the San Francisco Bay Area. Environ Health Perspect. 2006; 114(9):1438-44.
10           Hertz-Picciotto, I. et al. The CHARGE study: an epidemiologic investigation of genetic and environmental factors contributing to autism. Environ Health Perspect. 2006;114: 1119-25.
11           Hallmayer, J. et al. Genetic heritability and shared environmental factors among twin pairs with autism. Arch Gen Psychiatry. 2011(68):1095-102.

Autism Boom: An Epidemic of Disease or Discovery?

December 16, 2011 24 comments

Today’s “Got Questions?” answer is from Autism Speaks Chief Science Officer Geri Dawson, Ph.D.

Earlier this week, the LA Times ran a provocative article under the questioning headline above. It suggested that autism’s twentyfold increase over the last generation may be “more of a surge in diagnosis than in disease.” In fact, scientific evidence suggests that autism’s dramatic increase is only partially explained by improved screening and diagnosis.

Some of the clearest evidence of this increase comes from research documenting a 600 percent jump in autism caseload in California between 1992 and 2006. In related studies (here and here), Peter Bearman estimated that around 42 percent of the increase can be explained by changes in diagnostic methods and awareness with another 11 percent possibly due to increases in parental age at the time of conception (a known risk factor).

Taking into account all the factors that have been studied, this leaves approximately half of the increase due to still-unidentified factors. Through research, we’re increasing our understanding of these influences. For example, we now know that prematurity and extreme low-birth weight increase autism risk in babies. Certainly survival rates for premature and very low birth weight infants have increased considerably over the last twenty years.

While no single factor is likely to explain the marked increase in autism’s prevalence, researchers agree that a number of influences likely work together to determine the risk that a child will develop an autism spectrum disorder (ASD).

Bottom line: It is undeniable that more children are being diagnosed with ASD than ever before. The need for increased funding for autism science and services has never been greater. Autism costs society is a staggering $35 billion per year. And with more cases, that figure is likely to increase. Fortunately, there is clear evidence that earlier identification and intervention and supports throughout the lifespan can improve outcomes and quality of life.

If you are concerned about your child’s development, please see the “Learn the Signs” page of our website. If you are an adult struggling with issues that might be related to autism, please follow the hyperlinks to our resource page for adults and our page on Asperger Syndrome.

Got more questions? Send them to And join our next live webchat with Dr. Dawson and her co-host, Autism Speaks assistant vice president and head of medical research Joe Horrigan, MD on January 5th. More information on their monthly webchats here.

NBC’s TODAY show on South Korea Autism Prevalence Story

On Tuesday May 10  the TODAY show on NBC aired a discussion of the first comprehensive study of autism prevalence using a total population sample, conducted by an international team of investigators from the U.S., South Korea, and Canada. This study estimated the prevalence of autism spectrum disorders (ASD) in South Korea to be 2.64%, or approximately 1 in 38 children, and concluded that autism prevalence estimates worldwide may increase when this approach is used to identify children with ASD.  Watch the clip below.

For more information on this study, read a press release from Autism Speaks here.  Read coverage of the study from The New York Times here.

Vodpod videos no longer available.

It’s Time to Change the Conversation

February 17, 2011 143 comments

Autism Speaks recently declined an invitation to participate in a Dr. Oz show. In reviewing the pre-taping materials, it was clear that the program’s major focus was again on the vaccine debate, a debate that has been addressed multiple times, without resolution, and more importantly, a debate that prevents other equally important topics surrounding autism from being discussed. Last month, in a letter to the editor published by The New York Times, Autism Speaks’ Chief Science Officer Geraldine Dawson, Ph.D., said it is time now to focus our attention on the future and on the real problem: We still need answers to too many questions regarding causes and treatments for autism and we need to address the generation of a half million adolescents with autism who are about to enter adulthood without adequate supports.

Autism Speaks has consistently stated that children should be vaccinated to protect public health and the health of the individual child, and has urged families to develop a trusting and collaborative relationship with their pediatrician on all health matters including vaccination. While the Dr Oz show certainly makes for “Good TV,” this was not the televised conversation in which Autism Speaks believed it could make its most valued contribution on the science of autism. When “Good TV” presents “Good Science,” it makes an incredible difference for the families who struggle with autism and this is where we hope to be involved in the future.

In the short five years since Autism Speaks was formed, we have committed over $160 million in research on causes and treatments. In 2010, we analyzed the outcomes of the first 107 separate research grants funded by Autism Speaks and found that 82% of those completed studies resulted in 146 novel findings. We’ve “home grown” over 150 new scientists who are now committing their careers to the field of autism research. And even more impressive, for every dollar Autism Speaks committed to seed these innovative research projects, 10 dollars of additional research funding was leveraged in new grants from the federal government and other funding agencies.

Far beyond the research directly funded by Autism Speaks, there is new information and hope to share with parents. Effective diagnostics can identify infants at risk for autism as young as one-year old. We have learned that validated behavioral therapies can offer the best possible outcomes, particularly when started early, with such significantly increased cognitive, language and social skills, that in some cases, it may be possible for the child to no longer meet the diagnostic criteria for autism. The study of a wide range of treatments, including complementary and alternative therapies, will help parents find those that are truly effective to help them deal with medical conditions that so often are found in people with autism, from gastrointestinal to sleep disorders. Through Autism Speaks Autism Treatment Network, doctors are currently developing the gold-standard best practices for the treatment of the whole child with autism, which can be shared with practitioners in every town.

Autism Speaks sent a statement to Dr. Oz letting him know that we are eager to participate in a future program that focuses on how science offers hope for families. We encourage Dr. Oz and others in the media to feature the broader range of important issues facing families struggling with autism. These issues include:

·     The role of a multiple environmental factors that are potentially contributing to the increase in autism spectrum disorder (ASD) prevalence

·     New insights into the underlying biology of ASD that are leading to novel treatments

·     Ways we can address the medical conditions that impact the everyday lives of people with ASD, and

·     Programs that are being developed to help adolescents with ASD successfully transition to becoming happy and fulfilled adults.

Autism Speaks will always welcome the opportunity to talk about the scientific breakthroughs that are within our reach, and how by pulling together, we can advocate to increase research funding, end insurance discrimination, and create better services and support for people with ASD of all ages.

Evaluating Change in Autism Prevalence: Change We Can Believe In?

February 3, 2011 9 comments

This post is by Alycia Halladay and Michael Rosanoff, members of the Autism Speaks Science Team.

Twenty years ago, autism affected somewhere around 1 in 2000 children.  Today, it affects 1 in 110 children.  In other words, autism prevalence has increased dramatically over the past 20 years.  In fact, it has increased an estimated 600%.  Seems straightforward enough, yet why do we keep hearing the same question…

“But is it a true change in autism prevalence?”  That is, how much of the change in autism prevalence is truly due to an increase in autism risk?

In an effort to uncover the answers to this question, Autism Speaks and the CDC co-sponsored a workshop entitled “U.S. Data to Evaluate Changes in the Prevalence of Autism Spectrum Disorders,” held on February 1, 2011 at the CDC Headquarters in Atlanta, GA.

The “Evaluating Change” workshop was designed to bring together stakeholders from the autism community and thought leaders in the fields of autism epidemiology and public health to consider the factors driving the change in autism prevalence over the past two decades.  A growing body of epidemiologic research has begun to piece together the prevalence puzzle.  Factors such as younger age of diagnosis, broadening of diagnostic criteria, improvements in the availability of services, and better awareness of the disorder have all been attributed to the change in autism prevalence.  However, recent epidemiological studies indicated that, while these factors do account for a portion of the change, they cannot account for all of the increase alone (see Figure which was adapted from a presentation by Dr. Peter Bearman at the meeting).

So, where is the rest of the increase coming from?  What is causing it?  And most importantly, what can be done to identify and quantify the influence of multiple genetic and environmental risk factors, and their interaction, on the change in autism prevalence over time? (For more background, please see “What is Causing the Increase in Autism Prevalence”)

Scientists, advocates, family members, and individuals with autism alike served as expert panelists charged to identify promising directions, scientific priorities, and possible approaches for better understanding ASD prevalence trends in the U.S.  The beginning of the workshop focused on existing datasets that have been used to estimate autism prevalence and identify potential environmental risk factors associated with autism diagnosis.  These include:  the CDC’s Autism Developmental Disability Monitoring Network (ADDM), the California Department of Developmental Services (DDS) system, and Special Education data, as well as data from international health registries such as those from the Scandinavian countries.  These surveillance systems, while not designed to study the causes of autism, nonetheless have been helpful in identifying possible risk factors.  Not only have these resources provided information about the rising prevalence of autism, but they have also identified and replicated findings relating to parental age, obstetrical complications, certain chemical exposures and even genetic influences.

In addition to presentations on what has been already been done to understand reasons for ASD prevalence changes, examples of approaches to understanding prevalence changes from other health conditions were presented.  Scientists from the fields of cancer, Parkinson’s, asthma, and schizophrenia research presented methodologies and models for deciphering prevalence trends in their respective disorders and how these previous efforts may inform autism prevalence research.  In all cases it was found that changes in prevalence over time are often the result of a complex relationship between genetic and environmental risk factors, as well as factors related to diagnosis and awareness.

In the afternoon, participants broke out into discussion groups focused on the following topics:  1) How can prevalence information be used by stakeholders including parents, professionals, and policy makers?  2) What more  can be done with ADDM data?  3) Where are there other sources of data that can be used for prevalence estimates and 4) What else can be done to understand ASD trends?

As the discussions progressed, a number of overarching themes started to become clear.  Risk factors studied in isolation are going to underestimate their true influence.  They need to be studied in combination.  The influence of these risk factors is unlikely to be simply additive, and sometimes they will overlap.  Therefore, the field needs new analytic models that can study a combination of multiple genetic and environmental factors.  As Dr. Ezra Susser, from Columbia University said “It is helpful now not to look through the lenses of one side or the other, but rather both, and to use the information for better advocacy and awareness.“

Another participant, Dr. William McMahon from the University of Utah put it this way, “think of this black box of prevalence as a pinball machine.  You can’t predict the trajectory of the ball based on just one lever. There are dozens of other factors that influence where that ball is going to go”.

Other recurring themes included the need for data on well-defined autism phenotypes, as well as the importance of data quality and accuracy.

Throughout the meeting public attendees contributed their ideas through thoughtful, careful comments.  Stakeholders expressed their ideas and their hopes for the way prevalence data would be used – these included lingering and existing concerns about different environmental exposures, need for facilities for adults, societal treatment and acceptance, and reasons for differences in developmental patterns.

As understanding autism prevalence can help us identify priorities in research, services, outreach, and advocacy, the outcomes of this meeting will be published in a meeting report to inform future strategic planning.  This workshop was only a first step in better understanding the changes in autism prevalence over time and characterizing the potentially responsible risk factors.   Ultimately, as risk factors related to increased autism prevalence are uncovered and if those risk factors are modifiable, then researchers will have new targets for better treatments and prevention measures.  The bottom line is that the dramatic increase in the prevalence of autism calls for urgent action to understand why the increase in occurring.  It also underscores the crucial need for more and improved services to address the needs of people with autism spectrum disorders and their families.

Autism Speaks and the Centers for Disease Control and Prevention Announce Workshop

January 5, 2011 5 comments

Autism Speaks and the Centers for Disease Control and Prevention (CDC) are co-hosting a workshop that will investigate the changes in autism prevalence over time in the United States. Public Registration is Now Open.

Autism Speaks and the Centers for Disease Control and Prevention (CDC) are co-sponsoring a workshop to investigate the changes in autism prevalence over time in the United States.  The CDC currently estimates that 1 in 110 children (or approximately 1%) in the United States has an autism spectrum disorder (ASD).  This represents a 57% increase in ASD prevalence since the previous estimate just two years earlier.  Research over the last two decades has shown a stunning 600% rise in reported ASD prevalence over that time period and while new research is begging to uncover the reasons for this dramatic increase, many questions still remain.  (For more background, please see “What is Causing the Increase in Autism Prevalence”)

The purpose of this workshop is to identify promising directions, priorities, and needs for better understanding ASD prevalence trends.  The workshop will include presentations on what has been done to understand reasons for ASD prevalence changes, examples of understanding prevalence change from other conditions, and panel breakout sessions to allow for further discussions.

This meeting is open to the public with pre-registration required by January 24, 2011 for US citizens and January 13 for non-US citizens.  The workshop itself will be held on February 1, 2011.  You may find additional information below:

Date: February 1, 2011
Time: 8:00 a.m. – 5:30 p.m.
Location: Centers for Disease Control and Prevention
Roybal Campus
1600 Clifton Road NE
Atlanta, GA 30333
Tom Harkin Global Communication Center
Auditorium B

PLEASE NOTE: In person attendance for the workshop is limited to 180 people due to room capacity. Registration will close when capacity is reached. However, the public will be able to watch/listen to the workshop via webinar/phone, and registration for virtual attendance will remain open.

To attend in person, please visit:

To attend via Webinar, please visit

Are you finding that autism is increasing at the same/similar pace worldwide? I’ve read about pockets of increased autism in Silicon Valley, CA for example. Wondering if there’s data on a global rate of autism?

December 21, 2010 1 comment

“Got Questions?” is a new weekly feature on our blog to address the desire for scientific understanding in our community.  We received over 3000 responses when we asked what science questions were on your mind. We answered a few here and the Autism Speaks Science staff will address the other themes we received in this weekly post.

While we are seeing converging evidence in the research literature showing that autism prevalence is about 1% in developed countries such as the US and UK, there has yet to be published data on prevalence in low and middle income countries. Autism Speaks is actively trying to change that by funding epidemiologic research of autism prevalence in a number of low and middle income countries around the world including South Korea, Taiwan, Bangladesh, India, and South Africa. Conducting studies in countries where socio-cultural, environmental, and genetic factors may differ from those in the US can allow researchers to compare prevalence rates and examine how those factors may contribute to autism risk.


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