A Reason To Locate Autism's Hidden HordeAn article by Jonathan Mitchell
The 2003 update to the 1998 California report on autism begins:
The information contained in this report along with other formal epidemiologic studies confirms that the increased prevalence of autism in California is real and needs to be addressed.
This opening introduction to the report was prompted by the fact that the entry of persons with autism into the California State Regional Centers increased about 273% from 1987 to 1999. Between 1999 and 2002 these numbers doubled from more than 10,000 to more than 20,0000. Population based studies done as recently as the mid 1980s put the prevalence of autism at 4/10,000. A recent study done in the city of Atlanta by the CDC put the prevalence at about 33/10,000.
Although the California report starts out claiming that the increase in autism is real, it states later in a Note to Readers:
The information presented in this report is purely descriptive in nature and standing alone should not be used to draw scientifically valid conclusions about the incidence or prevalence of ASD in California.
The glaring contradictions of these two sentences shows that the question of whether or not there is a real epidemic of autism may be far from resolved. The question is whether or not there is a real increase in the incidence of autism caused by vaccines, other forms of mercury poisoning, or some other toxic agent in the environment or whether the greater number of autistic people is due to increased awareness of the disability, loosening of diagnostic criteria, recent federal special education legislation as well as changes in the service delivery system in the state of California.
Mark Blaxill, a parent of an autistic child and activist is among these people who are absolutely certain that there is a true epidemic of autism. One of the reasons is the failure of anyone to prove the so-called Hidden Horde hypothesis, i.e. that there are loads of undiagnosed cases of autism from the time period in which lower prevalence numbers were found.
Blaxill cites two different studies. One study done in North Dakota by Burd found a prevalence rate of 3.26 per 10,000 among children born in the area between 1967 and 1983. 12 years later a follow-up study was done of this same group of children and the results were that 98% of the children with autism born during this period in that part of the country were found. Only one autistic person had been missed. Another study was done by Nylander and Gillberg in Sweden. They screened outpatient psychiatric facilities in an attempt to find undiagnosed autistic adults. They managed to find 19 adults with autism who had not been diagnosed as children. The prevalence rates that they found were only 2.7 per 10,000. The prevalence rates in both these studies are far lower than what are being found today.
However, one must remember the old saw about looking for a needle in a haystack. The Sweedish study assumed that numerous adults with autism would present as outpatients in psychiatric settings. This may be an erroneous assumption, so the Swedish study may not offer the proof that Blaxill believes it does. Tighter diagnostic criteria and the absence of special education legislation that would have made identification of persons with autism more favorable may have accounted for the results of the North Dakota study. It is likely that case finding for those who did the Atlanta study was far easier. A large percentage of the autistic children was found in schools. The Individuals with Disabilities Education Act has made it easier to identify persons with autism who since 1991 have qualified for services under this law and would have reason to be identified. There were also numerous people with milder degrees of autism who were reclassified in the study. The study was also done under the auspices of the CDC so under federal law persons were forced to respond to surveys that they would not have been otherwise.
Because the statistics on autism in California and elsewhere have received so much publicity, epidemiologic studies in autism are now being pursued more vigorously than in the past in the hope to answer the question of whether or not the increase is truly real. These studies could aide in public policy and help make plans for the best service delivery for autistic children, present and future. Also, if the increase is real, an environmental trigger could be found and future cases of autism could be prevented. If there were a known environmental cause it might also lead to a greater understanding of the etiology of autism and perhaps lead to the development of more effective interventions than are currently available.
Are there compelling reasons to conduct epidemiologic studies with the intent of finding autistics in older populations? After all, they would be too old to benefit from any type of early intervention and there would be no need for planning of the service delivery system for these people. After all, most of them are now over the age of 21 and are no longer served under the IDEA. This might be the reason there are only two published studies in the literature on this topic, only one of them having been done in the United States.
This reasoning might be flawed. I believe that it is worth spending money and time to engage in case finding of persons with autism in older populations. If the autism epidemic is an artifact then a hidden horde might be out there and worth finding. Even if the epidemic is real, I believe it would be worth locating as many older persons with autism as possible, the older the better.
If breakthroughs in an understanding of the neurophysiology of autism were made it might be possible to find effective treatments or even a cure. Progress in uncovering the etiology of autism has been slow. To date there are no good animal models of autism. The symptoms of autism involve the unique human behavior of speech which does not exist in animals. Techniques used to image living brains may not yet be advanced enough to shed much light on autism's neuroanatomy. On MRI scans of autistic brains, Eric Courchesne found hypoplasia of the cerebellar vermis in lobules VI and VII. He found no pathology in lobules I through V. To date this work has not been replicated by any other researcher. The data from autopsies similarly don't jibe with Courchesne's findings. Neurologist Margaret Bauman has reported that on autopsies of autistic brains, abnormalities were found in the olive of the cerebellum and in the deep cerebellar nuclei. Yet the vermis, including lobules VI and VII, was the most normal part of the autistic cerebelli.
The best way to go may be autopsies of autistic brains. On autopsies abnormalities have not only been found in the cerebellum but also in the hippocampus and the amygdala as well. However, autopsies have not come close to resolving the exact etiologic nature of autism. To date only about 30 or so post-mortem autistic brains have been studied. Autism was first described in 1943 by Leo Kanner. The children he described were born in the 1930s and most of them are probably no older than 70 years old. Persons with autism have a normal life expectancy. Therefore, there is a dearth of brains available for post-mortem autopsy.
The question is whether or not it is possible for the neuroanatomy of autism to be well-understood if enough brains were available for autopsy. The answer may well be yes. Take Parkinson's disease for example. Based on autopsies that have been done we have a good understanding of what is going on in the brain of a person with Parkinson's disease. It is known that Parkinson's results from damage to a brain structure called the substantia nigra as well as to a tract called the nigrostriatal bundle which travels to an area of the brain called the globus pallidus which is part of the basal ganglia. The neurotransmitter dopamine is involved in these areas of the brain. Therefore, medications which increase the production of dopamine are effective treatments for Parkinsonism. Unlike persons with autism, whose condition appears before the age of 3, a person with Parkinsonism usually does not develop symptoms until after the age of 50. Also, unlike autism, Parkinson's is a progressive disease whose course worsens with time and often results in an early death of its victim. Therefore Parkinson brains have been available for autopsy, making the etiology well understood. There was also no "bad mother" theory for Parkinson's to impede progress into its neuroanatomical basis the way there has been for autism.
Perhaps if enough autistic brains were available for autopsy, we could uncover the cause of autism and know exactly what is happening in an autistic brain. The Burd study only examines persons born in the year 1967 and later. But what about persons born before 1967? What about persons near the end of their life, those born in let's say the 1920s or earlier. The example of Max Weisberg comes to mind. Weisberg was a mildly mentally retarded man who gained notoriety as a bookmaker. He was a savant whose extraordinary skills with numbers resembled a true Rainman. He was able to apply these skills as a bookmaker, making thousands of dollars, and largely avoided prosecution due to his being retarded. He was born in 1924 and died last year of pancreatic cancer. No mention is made of the possibility that he was autistic in any of the articles written about him. What if Mr. Weisberg had been born in 1984 or later instead of 1924? Would he have been diagnosed as autistic? It is quite possible if not likely that he would have been. Studies have shown that about 10% of persons with autism have savant skills of some sort, e.g. extraordinary photographic memory, ability to tell what day of the week a date falls on, extraordinary musical ability, etc. The percentage is less for people with general mental retardation.
How many undiagnosed persons in this age range are out there? Is there some way they could be found through more aggressive case finding than Burd and Nylander pursued in their studies? If Weisberg and others like him had willed their brains to science would we be closer to finding some true answers to the puzzle of autism? Perhaps this is the case. It could be that our priorities are mixed up and there should be more funding of epidemiologic studies of autism in as old populations as possible.
|Copyright 2006, Jonathan Mitchell - All Rights Reserved.|