Age of Diagnosis and the Apparent Increase in Autism
December 2, 2008 by Kristina Chew, PhD
Filed under Health
When Charlie was formally diagnosed with autism in July of 1999, “autism” seemed like something strange and puzzling and (to be very honest) unfathomable to me. I didn’t know anything about it, and I didn’t understand why it was necessary to apply such a “label” onto my toddler.
Nine years later, and not only do I know a great deal more about autism (with much more still to learn). It seems that people in general know a lot more autism, or are at least familiar with the word; it’s been some time since I said “autistic” and someone said back to me, “You mean he’s artistic?”.
At 10 months, Charlie’s then-pediatrician noticed that he had a “minor gross delay”: He’d just started rolling over at 9 months and, too, just started to sit independently. He had other gross motor delays and, taken on their own, these didn’t, and don’t, add up to an autism diagnosis. But Charlie, as I realize in thoughtful hindsight, did not display joint attention. He loved to be carried and held and smiled; he tended to stay put in one spot. Now, every time I read about some researcher’s latest new method for identifying autism in infants, I wonder, what would such a test have noted about Charlie? And I as often think, it’s likely they would have noted “something” about Charlie—-that, today, he might have been diagnosed at an even younger age; researchers are, indeed, evaluating the accuracy of autism screening tools for children 18–24 months of age.
A study in the December Archives of Pediatrics and General Medicine examines autism prevalence trends over time in Denmark and states that “the apparent increase in autism in recent years is in part attributable to a decrease over time in the age at diagnosis.” A cohort of more than 400,000 children—all children born in Denmark from January 1, 1994, through December 31, 1999—were studied. From the abstract:
Results Statistically significant shifts in age at diagnosis were observed for autism spectrum disorder; children diagnosed before age 9 years in the cohorts born between January 1, 1994, and December 31, 1995, between January 1, 1996, and December 31, 1997, and between January 1, 1998, and December 31, 1999, were on average diagnosed at ages 5.9 (95% confidence interval [CI], 5.8-6.0), 5.8 (95% CI, 5.7-5.9), and 5.3 (95% CI, 5.2-5.4) years, respectively. The relative risk comparing the 1996-1997 birth cohort with the 1994-1995 birth cohort at age 3 years was 1.20 (95% CI, 0.86-1.67), which decreased to 1.10 (95% CI, 1.00-1.20) at age 11 years. Similarly, the relative risk comparing the 1998-1999 birth cohort with the 1994-1995 birth cohort at age 3 years was 1.69 (95% CI, 1.24-2.31), which decreased to 1.23 (95% CI, 1.11-1.37) at age 11 years. Similar results were observed for childhood autism.
Conclusions Shifts in age at diagnosis inflated the observed prevalence of autism in young children in the more recent cohorts compared with the oldest cohort. This study supports the argument that the apparent increase in autism in recent years is at least in part attributable to decreases in the age at diagnosis over time.
When Charlie was just diagnosed and shortly after (in 1999-2000), we were often told that he—he was 2-3 years old then—was “very young” to be diagnosed. Now, it seems standard for children to be diagnosed by the time they’re the age Charlie was when he was diagnosed with autism back in 1999. It seems more than obvious to me that we would have been told that they were seeing “red flags” about, who knows, 6-month-old Charlie’s development, and we would have started out on the road to a diagnosis even earlier than we did. A summary of the articles in the December Archives of Pediatrics and General Medicine displays two graphs, which show that, between the two birth cohorts studied (one from 1994-1995 and the other from 1998-1999), the age of a child at the time of autism diagnosis decreased, even as the prevalence rate has been increasing.
Again, the authors of the study note that it’s possible that “the apparent increase in autism in recent years is at least in part attributable to decreases in the age at diagnosis over time.” Thus, early detection and diagnosis of autism—-and increasingly earlier detection and diagnosis, at that—are, it can be argued, contributing to the increase in the prevalence rate of autism. Our ability to better diagnosis autism isenabling us to identify autism earlier in younger children and this is a contributing factor to the rise in autism cases. There’s not so much an “autism epidemic” occurring, as that our knowledge about autism is growing and will, it seems and I hope, continue to.
Early diagnosis is often talked about as the ‘gold standard’ and what we should be striving for. I don’t know enough to agree or disagree but I have to say that our diagnosis at the age of 4 was probably just about right for us. Interesting study though.
I think also that parents are better educated about child development now a days and are more aware of what a child should or shouldn’t be doing at a certain age (thank you “what to expect” books and the like). So parents themselves pick up on things earlier.
Sorry, I don’t buy it. Genetics says that if this is true then I should have autistic people in my family and my wife’s family. But we never heard of autism or knew what it was or anyone who fit the diagnosis when we grew up. The claim that the increase in autism is due to a change in diagnostics is just wishful thinking.
My students were reading an essay on the difference between tragedy in the ancient world and in modern times. We were using Sophocles’ tragedy Antigone as our example. Soren Kierkegaard was the author of the essay; he distinguished between the ancient view of tragedy, which is caught up in notions of the “curse on the house[hold” and of fate, while the modern notion refers to an individual and the choices that he or she makes (Willy Loman from Miller’s Death of a Salesman was our example of a modern tragedy). In discussing Antigone, students tended to talk about the “choices” she made and how she operating our of her own motives as an individual to do right, and they were thoughtful, and a bit perplexed, when I pointed out that they were applying a contemporary understanding of the tragic onto Sophocles’ ancient Greek play.
It’s not easy to see out of one’s historical moment; in the case, that would mean, to imagine a world and culture without current definitions and the current understanding of autism.
Just thinking.
“Genetics” does not always refer to hereditary genetics. There are also genetic anomalies, genetic damage, genetic triggers, and many other ways to describe irregularities in the genetic code.
There are correlations in autism that are equal to or greater than correlations of other genetic conditions:
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1196434
Among the five BPASS (DSM-IV autism) traits that were analyzed, the traits for social motivation and range of interest/flexibility show the highest heritability (0.19 and 0.16, respectively) and also have the highest genetic correlation (0.92). This finding suggests a shared genetic basis of these two traits and that they may be most promising for future gene mapping and for extending pedigrees by phenotyping additional relatives.
Even though the etiology of this disorder is unknown, evidence for genetic influence is strong. Multiple studies report that MZ twins are 60%–95% concordant for autism (Folstein and Rutter 1977a; Ritvo et al. 1985; Steffenburg et al. 1989; Bailey et al. 1995). DZ twins and siblings have much lower concordance rates: estimates range from 0% to 24%, with most between 5% and 10% (August et al. 1981; Smalley et al. 1988; Bolton et al. 1994; Bailey et al. 1995). Together, these MZ and DZ sib concordance rates indicate that both genetic and environmental factors contribute to disease risk.
Though twins correlate, there is only minimal evidence of direct inheritance of classic autism. It is when we apply the broader autism spectrum that we locate the 92% (.92) correlation between multi-generation comparisons (one generational skip or less).
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While a .19 correlation might seem like nothing to most people, in science it is a major indication of association. When nearly 20% of a group have a relative with the same condition, that is much higher than random odds. The 92% correlation among twins with severe autism is even harder to ignore.
- CSW
“But we never heard of autism or knew what it was or anyone who fit the diagnosis when we grew up.”
Neither did I, yet here I am working in an autism service that has several people my own age and older, who are very classically autistic, including several from my home town.
A claim from personal experience is never impressive, as it only holds validity if one presumes that your ability to recognise a person with autism is the same then as it was now, and only if you presume that the social and institutional factors involved haven’t changed.
Both of this presumptions are extremely niave and very likely to be wrong.
@Dedj
I am not the only one to have seen this. The lady who ran the treatment center that my son attended is qualified to recognize autism. Her words did not only express doubt.
It is not naive to know that the statistics on autism had been 1 in 2500. It is not naive to notice that the three elementary schools nearby all are dealing with classically autistic children and none of them have more than 250 students. It is not naive to see the claim that autism is just diagnostics is made without proof. It is not naive to recognize that being “just diagnostics” takes the pressure off the pro-vax crowd to find something that fits the geography and the timing besides vaccines. It is not naive to notice that the ones who espouse this theory are almost exclusively pro-vax. If you want to be naive, then accept the autism epidemic as being “just diagnostics” on faith.
As someone who worked with special needs children in the 1970’s, or “exceptional” children as they were known then, I can say that we didn’t have a single child with autism among those who were in our program. However, there were many “brain damaged” and “emotionally disturbed” children, and guess what kind of behaviors those children had? If you guessed repetitive you would be right. Maybe you’d like to guess what kind of social and language skills they had as well?
I do not know of a better source of statistical data than that which was collected by the California school system. If you went to the California statistics, you would find that the autism rate went up when the other diagnoses remained steady. The ones who collected the statistics concluded that it is not diagnostics.
@Ed
It should be noted the twin meta-studies of the NIH/CDC state (quoting what I pasted earlier): “concordance rates indicate that both genetic and environmental factors contribute to disease risk”
I honestly have no vested interest in what the underlying causes are, including any environmental triggers. What I care about is developing the best educational approaches for middle school and secondary students. I definitely see a lot of families with traits of autism in siblings, parents, cousins, et cetera.
We also increasingly diagnose “twice exceptional” (2X) students who are both gifted and high-functioning (PDD-NOS, HFA, AS). These students were not cataloged in the past. Their parents, often gifted professionals, are also curiously “quirky” and might be assessed with AS — or at least ADD/ADHD.
My own classification changed every few years. In 2006 I was moved from “brain trauma” to “high-functioning” at the age of 38. The university has scheduled yet another assessment for this December, when for all I know things will be “revised” again to either AS or backwards to ADHD/Seizure Impaired.
Honestly, my own experiences simply demonstrate that diagnostic criteria and the resulting labels over 40 years continue to evolve. Since my degrees are not in psychology, I have to defer to the assessment teams we use.
Still, I think my “gut instinct” about the parents I meet is pretty good. “Quirky” physics professor with “AS” child… trust me, they are similar.
@C.S.
The fundamental argument in all of this is whether there are any environmental contributors to the level of autism. Denial of any epidemic means that no environmental contributor needs to be found. Denial is part of the pro-vax creed. I call it a creed because it was offered and accepted on faith and without proof.
This creed is necessary because any environmental contributor must meet the criterial of space and time. The pro-vaxers have no contributor to offer that fits this criteria and vaccines keep rushing in to fill that vacuum no matter how many articles, no matter how many expert opinions to the contrary.
This is frustrating whether vaccines contribute to autism or not. If vaccines contribute to autism then denial that there is anything environmental hurts the autism community. If vaccines do not contribute to autism then denial that there is anything environmental hurts the autism community.
As noted before, I don’t think Charlie — who most people say now is “classically autistic”—-might have received such a diagnosis in previous years; more likely, he would have been considered mentally retarded, with emotional behavioral disorder.
@Kristina
Do you think the “label” matters to your understanding of Charlie as your son? I don’t mean that to sound rude or offensive — I am trying to consider the “rhetorical implications” (uhg) of the word “autistic” as experienced by parents.
I know the label matters in terms of what I can or cannot provide to students. Labels determine access to extra help, even at the university level. But, labels seem fluid, ever changing as we learn more about the mind. What is “autistic” today might be three or four different things in two decades.
@CS Wyatt,
At the time when he was diagnosed, the labels meant a lot. I was really afraid (that is the best way to put it) about saying he was mentally retarded. It’s perhaps ironic that there has never been a question about Charlie having the autism “label”—he’s always been “autism,” not PDD-NOS, not “mild autism.” Again, when he was younger, these differences were something to get used to; as things have turned out, it’s been a lot “easier” (from the perspective of getting services) that Charlie’s diagnosis has not been in question.
“Rhetorical implications”—-paper you’re working on?
Ed – like it or not, it is niave to believe that the definition of autism has not changed since you were at school. Hell, it changed radically the year I left mine.
It is niave to believe that several legions of relevantly qualified and experienced professionals would merely accept the ‘diagnostics’ idea just on someones say so. It is also niave to believe that claim is made without evidence, especially as some of that same evidence is what led to the diagnoistic criteria being what they are now.
It is incredibly niave to believe that the social and institutional changes – most noticably the drive to mainstream special needs children – have had no impact on their appearance in mainstream schools. Certainly, some of the older clients I work with would never have been mainstreamed at all, yet some of the younger clients are assisted to go to college (high school) and some eventually go to onto Uni (college) with support.
This matches my experience with dyslexia exactly – less than 10 or so out of a 600+ school in the early 90’s, yet I’m now in contact with twice that number, most only being assessed in adulthood regardless of being fresh from A-levels or being parents of teenagers.
I think you’ve hit the nail on the head as to why the anti-vax idea still has support – people simply won’t pay any attention to the evidence against them. Environmental issues may play a factor in autism , but to deny that the diagnostics have radically changed and improved is not just niave but is actually quite stupid.
This is why claims from personal experience hold little validity – anyone can claim anything, especially if they retrospectively attribute skills of perception and comprehensive experience to themselves. Your experience is exactly what you should expect it to be regardless of wheter it’s ‘diagnostics’ or ‘epidemic’.
@Kristina
No, no paper planned on the specific question, but it is haunting me, lately. The university wants me retested and this neuro-psych team seems to think I can’t be HFA/autistic and be a student of rhetoric and philosophy. You know “autistic” means I can’t possibly deal with abstractions.
If I am “relabeled” it will be frustrating. It gets tiring to be categorized every few years. I went from remedial to gifted to “average” to gifted with ADDD… and so on… throughout school. The bouncing about has affected how I view the labels — unreliable and subjective.
Instructors do judge you by the labels. Peers also judge you. I guess I can’t help but wonder how the label changes influenced my parents over the years.
It is apparently okay to also be interested in science. The neuro-psych team seemed to approve of my scientific pursuits, as if that fit with “ASD.” It’s as if they have a template I need to match.
Changing criteria, changing “rates” of autism. We’re a moving target, I guess.
Dedj,
In Dr Chez book “Autism and its medical management”, he talks about a meeting with other pediatric neurologists. These are people who would recognize autism if they saw it. When asked who was treating autism 20(?) years before almost noone stood. When asked who is treating autism now, all stood.
I believe his testimony and I do not believe Dr. Offit who offered the theory in his False Prophets book without proof.
I believe his testimony too, it’s what’s been happening across the board, for all professions, for most neurological conditions I can think of, even those that have decreased in incidence. It’s a predictable and totally expected experience.
I’ve worked with plenty of people whose care needs were met by a very small team of people, because that was the only people willing to do so. Now with the push for mainstreaming they get taken care of by their GP or down the local hospital, just like anyone else.
The question is why the exposure has changed, not wheter it has, as exposure would change for the reasons put forth by the autism community. Unless you can show that none of the other contributory factors have changed (tip : the general consensus in the autism field is that they have changed rather noticably) then your example is as much an arguement in favour of Dr Offit as it is against it.
I’ve not read False Prophets yet, but I strongly doubt Offit failed to provide references. It’s irrelevant anyway, he’s reporting consensus, not making it.
The main questions to ask anyone claiming increased exposure are these:
Is the definition of the condition under scrutiny the same? If so, can we expect lesser or greater exposure if all other factors were the same?
Has the opportunity for exposure remained the same? If not, have services changed? If so, are they now more delineated or inclusive?
Would the person have had proper awareness of exposure at the time? Could they be motivated to remember otherwise?
That’s just a shortlist of questions to consider when reading opinion. McMasters or CASP can provide good templates for other critiques.
We need to consider all factors and not just jump to the conclusion that it must be increased incidence just because some guy took a straw poll one day.
Sorry, add “, even when that some guy is an authourity” to the end of the last sentence.
Dedj,
It is a matter of faith that there is no epidemic. This is necessary for the pro-vax community since they have nothing to offer to replace vaccines as what caused the epidemic. It does not mean that there can be nothing else, but every time there is a mention of an autism epidemic and the pro-vax community says it can’t be vaccines, with nothing else to replace it vaccines rush back in to fill that void. Faith doesn’t make it.