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Guest blog: New normal

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Walter Zahorodny
29 January 2013

In 2007, when the Centers for Disease Control and Prevention’s (CDC) Autism and Developmental Disabilities Monitoring Network — of  which I am a member —  published its autism rates for 2000 and 2002, New Jersey’s autism estimates were among the highest in the country — about one percent (1 in 94 children), compared with an average of 0.67 percent in other network states (1 in 150 children). 

At the time, New Jersey’s rate was considered high. The CDC’s current nationwide estimate for autism is 1 in 88 children, or 1.1 percent. New Jersey’s rate has also risen, to 1.7 percent.

The findings raise the question: Was New Jersey more effective than its counterparts at accurately detecting autism, and detection methods elsewhere have simply caught up? Or are there some special factors contributing to greater autism risk in New Jersey?

Our findings add weight to the possibility of a true increase in autism prevalence and suggest that the true scope of the disorder may be larger than ever imagined. 

The reasons for New Jersey’s levels at the turn of the millennium were unclear, but at the time there was reason to believe they were related to more accurate detection of autism cases.

Our research team had access to more high-quality information than investigators in other states did, largely because New Jersey was ahead of its time in employing multidisciplinary teams of experts in evaluating children for special education services.  

Moreover, high levels of autism awareness and the availability of autism-specific resources in New Jersey predated the monitoring period. This increased the likelihood that parents and physicians would detect children who showed signs of the disorder.  

Premature prediction:

Before analyzing data for the subsequent surveillance period — 2002 to 2006 — our researchers anticipated that autism prevalence would increase slightly in our state and rise more sharply, though moderately, in other network states. 

There had been no major changes in autism diagnostic criteria, service eligibility or access to resources between 2002 and 2006. If New Jersey’s elevated autism rate was mainly due to better detection, we reasoned, other states’ autism rates would rise over time to the level identified in our region as their detection methods improved. 

It turns out this prediction was wrong, or at least premature. 

Autism prevalence rocketed upward — both in New Jersey and nationally. In our state, rates rose to 1.7 percent (1 in 57), including 1 in 35 boys, with increases across all demographic groups and most autism types.

Interestingly, neither changes in community diagnostic practices nor improved detection seem to have played a large role, as shown by district-to-district comparisons and analyses of data quality. 

What’s more, across the 2002 to 2006 period, more than 70 percent of all the New Jersey autism cases satisfied the diagnostic criteria for Autistic Disorder, the most comprehensive form of impairment. That contradicts the possibility that the rise represents better detection of more subtly affected children, rather than a genuine change in prevalence. 

Unfortunately, the relevant risk factors are not yet known. Preliminary information suggests that the rise may reflect a combination of demographic and perinatal factors. Our group is conducting studies to assess those factors. 

If New Jersey is a leading indicator of autism prevalence, we should anticipate two percent rates across the U.S. Whatever the causes, this level of autism prevalence cries out for the development of resources for these children, and for ramping up consideration of environmental influences, such as maternal health factors, on autism risk. 

Walter Zahorodny is assistant professor of pediatrics at the New Jersey Medical School - University of Medicine and Dentistry of New Jersey.

News and Opinion articles on SFARI.org are editorially independent of the Simons Foundation.


Name: Twyla
31 January 2013 - 4:15PM

Two possibilities:
Unlike many states, New Jersey does not have a "philosophical" vaccine exemption, and may have higher rates of compliance with the entire CDC vaccine schedule.

New Jersey may have a higher rate of mercury in the environment due to being home to many pharmaceutical companies which over the years have disposed of thimerosal (a vaccine preservative containing 49.6% ethyl mercury).

An interesting story about Brick Township, N.J.:
Part 1
Part 2

Name: Matt Carey
5 February 2013 - 8:04PM

For the record, New Jersey has one of the lowest uptake rates for vaccines in the U.S.

If vaccines were a major factor in the increase in prevalence over time, we'd expect Alabama to have the higher rate (it has a low reported rate).

Name: Walter Zahorodny
31 January 2013 - 7:52PM

Given considerations of time, resources and ability to capture reliable case-specific information about vaccine use and mercury exposure, it seems to make sense to investigate maternal health and perinatal risk factors for autism.

Name: Meryl Dorey
31 January 2013 - 9:21PM

Fantastic article, Dr Zahorodny. One question - would you support a study of the rates of autism in those who have been vaccinated according to schedule vs those who are completely unvaccinated? It seems that this would be a relatively cheap study to perform and would indicate whether or not further research into the link between vaccines and autism would be warranted. According to several preliminary surveys, it appears that the rate of autism in the completely unvaccinated is close to zero - we already know how high the rate is in the fully vaccinated. Don't you think a study such as this is well overdue?

Name: Walter Zahorodny
4 February 2013 - 10:07PM

Meryl, It might not be so easy to conduct a study that looks at this question in a rigorous, unbiased, manner, but I'm all for it.

Name: Matt Carey
5 February 2013 - 8:01PM

I would question whether we really know the prevalence of autism. We are still catching up, and only one study in recent times has attempted a whole-population methodology. That study (Kim et al) found a much higher prevalence than most other studies, and ADDM sites report large numbers of individuals who were previously unidentified.

As to the notion that some surveys have shown low prevalence in the unvaccinated population, this simply isn't true. One very poor survey was created by Generation Rescue which showed higher rates in the unvaccinated. There has been some very poor journalism purporting to show low prevalence in supposedly unvaccinated populations, but that was (a) journalism and (b) of low quality.

The idea that this would be a relatively cheap study to perform is not accurate, either. Doing a study well to correct for confounds would be difficult. One attempt, presented at IMFAR recently, showed a *higher* prevalence among unvaccinated children. The reason proposed by the authors was parents forgoing vaccines for younger siblings of autistic children.

Two ideas were proposed for the vaccine hypothesis. Mercury and MMR. Both are clearly not responsible for a significant increase in autism risk. I have not seen any individual or group promoting vaccine causation which has accepted those facts.

There are so many places to look for answers. Going over the same territory doesn't strike me as a valuable use of limited resources. Going over even less thought out hypotheses also does not strike me as a valuable use.

Name: Walter Zahorodny
7 February 2013 - 8:48PM

Matt, The (2006) ASD rate among boys in NJ is in the same range as reported by the Korean study. Though we do not breakout our data by town or district for publication, there have been areas in our region with ASD rates higher than 3% since the 2000 study year and the number of towns with > 3% rates has increased. In general, the more careful the method, the higher the rate.

Name: passionlessDrone
5 February 2013 - 6:50PM

Dr. Zahorodny -

Thanks for this article and your responses. My memory may be failing me, but is it correct that the ADDM reports sometimes utilize different states; i.e., the ADDM reports in 2002 and 2006 included different geographical areas. Understanding that there is significant variations at the state and community level in diagnosing autism, could you speak a little toward the changing data set between reports? Figuring out how much, if any, of the rise in prevalence represents a rise in incidence is already plenty difficult; it seems like shaking the underlying data up and down introduces another problem.

Regarding data collection on perinatal influences, that definitely sounds interesting. Can you give us some insight into the kinds of things you are chasing?

Name: Walter Zahorodny
7 February 2013 - 7:48PM

Dear Drone, The ADDM reports have included different states, as the surveillance network has changed over time. These variations were a byproduct of funding decisions by CDC. The comparisons in ASD prevalence between 2002 and 2006 and 2002 and 2008, reported in (MMWR) March 2012 involved adjustments such that only areas which were surveyed in the reference years were compared. This restriction was undertaken to increase the reliability of the trend findings, that is that the findings reflect a true increase. I do agree that the clarifications and analytic restrictions make the report more difficult to read. We intend to look at a number of perinatal factors, including maternal health, mode of delivery, multiple gestation and neonatal complications and interventions.

Name: Matt Carey
5 February 2013 - 7:42PM

"What’s more, across the 2002 to 2006 period, more than 70 percent of all the New Jersey autism cases satisfied the diagnostic criteria for Autistic Disorder, the most comprehensive form of impairment. That contradicts the possibility that the rise represents better detection of more subtly affected children, rather than a genuine change in prevalence. "

Could you clarify? From what I see in the 2008 report

New Jersey reportd 19% with autistic disorder, 71% with ASD/PDD, and 9% Asperger. The fraction with autistic disorder in table 3 is the lowest in New Jersey of the ADDM states.

Also, the fraction of autistics identified with intellectual disability is low in New Jersey compared to other ADDM states.

The average across all states for the 2008 report was 38% with ID. New Jersey was 27%. It would be interesting to see how that fraction has changed over the various ADDM report years.

It is very clear that in the US many autistics have gone undiagnosed, and this is almost certainly still the case. Even in New Jersey, the fraction who had no mention of ASD in their records prior to ADDM review as over 15%.

Many online discussions get caught in a false dichotomy: either there is a shift driven by social factors (e.g. better ascertainment) or there is a true increase in the fraction of individuals in each cohort who are autistic. There can be both. We know there is a shift due to social factors, and there is a high probability that there is a true increase due to older parents.

It is important to look for risk factors. It is also important to support the autistic population today.

Name: Walter Zahorodny
7 February 2013 - 8:40PM

Matt, More than 70% of all the NJ surveillance-determined ASD cases satisfied the DSM-IV-based definition for Autistic Disorder, regardless of study year. In the 2008 report, the 19% w Autistic Disorder, 71% w ASD/PDD, etc.. refers to the diagnoses of record among (NJ) cases who had an ASD diagnosis from a community-based clinician. This points to the fact that clinicians overuse the PDD diagnosis. That is well-known and part of the rationale for the proposed DSM-5 changes in ASD definition. It is true that we identify more ASD children w IQ > 85 than some states, but we are in the range of other states (Arizona, NC, Utah). I expect that the proportion of ASD children w IQ > 85 will shift upward, as states' school and health authorities (and the surveillance teams) get better at identifying them. I agree that many discussions are caught in the either/or dichotomy. Both better awareness of ASD and true increase in prevalence are likely. It is important to systematically investigate ASD risk factors and to use and clarify these findings so as to improve care and support for all affected individuals.

Name: Matt Carey
8 February 2013 - 10:06PM

Thanks for that clarification.

Sue Swedo spoke before the IACC last July on the DSM 5. One example she gave was my home state: California. She reported that in California most ASD diagnoses are autistic disorder and speculated this is because the law here was never updated for the DSM IV, so only "autism" is mentioned as a qualifying category for services.

One point I would also make is that it isn't so clear that "autistic disorder" represents "more subtly affected" individuals. Richard Grinker made the point in a NY Times piece years back. He used his daughter (who has a diagnosis of autistic disorder) and a classmate (with a diagnosis of Asperger). The classmate in many ways had more challenges than his daughter.

In the end, we are talking about a very broad spectrum. While I recognize that an individual one might consider "typical" or average autistic is not the same as an individual one might call "classic" autistic.

This causes some concern for many who, like me, are parents of children with ID and other challenges in addition to autism. Many are concerned that the shifting demographics will result in those with ID being sidelined in focus and advocacy.

Name: Mena
6 February 2013 - 1:51AM

While we can debate whether there has been a true increase, I think everyone can agree that the prevalence is high at 2%, and risk factor studies are necessary to understand the causes.

Name: Matt Carey
6 February 2013 - 5:59PM

I don't see why "high" or "low" plays into whether one looks for risk factors. Of course we look into risk factors.

I do think if we assume, as we should, that 2% of the population is autistic, then we are only identifying a fraction of that population, we are (a) missing a lot of information which can assist autistics and (b) we are failing to support autistics today.

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