If it seems like most of the people you know with autism are 22 or younger, that's because most people diagnosed with autism were born after 1987. A recent US EPA study has found a distinct "changepoint" year - or spike - in autism in California and elsewhere and concludes that it would be "prudent to assume that at least some portion of this increase is real and results from environmental factors."
"In the Danish, California, and worldwide data sets, we found that an increase in autism disorder cumulative incidence began about (the birth cohort years) 1988-1989," wrote the authors Michael E. Mc Donald and John F. Paul, of the EPA's National Health and Environmental Effects Research Laboratory.
"Although the debate about the nature of increasing autism continues," they added, "the potential for this increase to be real and involve exogenous (external) environmental stressors exists."
But it was the distinct timing in the increase of autism - the birth of an epidemic, as many believe - that was most notable, and which "may help in screening for potential candidate environmental stressors."
"The calculated year was determined to be significant," the EPA scientists said. The rate of increase before 1988 "was significantly different" than the rate after that year (the "postchangepoint," in epidemiology parlance). In California, the rate spiked from 5.7-per-10,000 before the changepoint, to 20.8-per 10,000 in its wake, and the worldwide dataset showed a similar jump (from 6.0 to 24.2). In Denmark, the rise was even more dramatic, though total incidence was only a fraction of that in the US: from 0.6 to 6.6.
(A study in Japan from 1988-1996 showed continuously increasing autism rates, but no calculable changepoint year - please see the full report for a discussion on study limitations).
So why would rates more than triple in California kids born before and after 1988? Is it just the result of better diagnostics and better reporting, as many have insisted? Or did something drastic change in these children's environment, beginning in 1988?
The EPA officials doubt it was the former. They noted a recent study suggesting that changing diagnostic criteria may account for only a "2.2-fold higher cumulative incidence of autism, relative to the seven-fold increase" reported in California over 11 years. Likewise, they said, "diagnostic substitution," or switching kids from the mental retardation to autism category, "could not account for increased autism from 1987 to 1994."
As they wrote:
Although artifacts associated with observed increases in various studies cannot be ruled out, from a precautionary standpoint, it seems prudent to assume that at least some portion of this increase in incidence is real and results from environmental factors interacting with susceptible populations. As such exposure is potentially preventable, identification of relevant candidate environmental factors should be a research priority.
Meanwhile, the scientists were surprised to find such similar changepoint years in California, Denmark and the worldwide dataset, although they conceded the data were consistent with similar studies done in Minnesota and Sweden, and a third US nationwide study which found, "the greatest increase in ASD prevalence occurring in cohorts born between 1987 and 1992."
There are many external factors that could be associated with autism, the authors said, so knowing when the explosion in cases began should help narrow down the long list of suspects.
"Future studies should examine for novel or increasing exposures to environmental factors from gestation to at least age three for our calculated 1988-1989 birth cohorts," the authors wrote. "Assuming a dose-response relationship, a candidate factor would have continued to increase in the environment from the late 1980s through at least the mid-1990s."
But what could it (or they) be? According to the EPA:
- Any candidate must be a substance or substances whose exposure level dramatically increased in developed countries beginning at the 1988 changepoint.
- The candidate will likely be something whose exposure level was greater in California than in Denmark between 1988 and 1997.
- The candidate is likely something that was introduced in developing countries later than California, Japan and Denmark. For example, a recent Hong Kong study "is suggestive of a rise in autism, but beginning more recently than our calculated changepoints."
- The candidate "would need to be disruptive to early human neural development."
- The candidate would need to have a route of exposure "consistent with bioavailability to fetuses and infants."
- The candidate would need to have increasing levels of US exposure between 1988 and at least 1995.
- The potential for exposure to a variety of environmental factors "acting synergistically on susceptible populations also cannot be ruled out."
The authors suggested an initial toxicological screening for potential autism-trigger candidates using the CDC's Agency for Toxic Substances and Disease Registry or similar data sets.
The EPA officials did not offer a list of substances that should be looked at, though they did note that studies on MMR vaccine and the mercury-based vaccine preservative thimerosal, "did not support a relationship with autism," including a 2004 report from the Institute of Medicine.
No studies have been done on other vaccine ingredients and autism risk, however, nor on the entire vaccine schedule.
If no candidate pans out as the culprit, they wrote, "perhaps most of the observed increases are not caused by an environmental factor, but result from study artifacts that produce false increases or from the current levels being correct but not a true increase."
Either way, the current caseload is going to cost a fortune. People with autism in California born between 1988 and 1997 will incur a mean lifetime care cost between $2.7 billion and $4.0 billion, and "these costs likely have continued to grow in recent years."
I am hopeful that this information will finally spark the mad-dash that this country desperately needs to make to identify the environmental factors in autism. We require a Manhattan-Project style operation spearheaded by the Federal government, and we needed it ten years ago. This crisis is too serious to ignore in mild complacency any longer.
Here are just some of the areas where science is looking:
AIR POLLUTION - A few studies have linked increased risk of autism to environmental toxins - such as mercury - in air pollution, including a CDC funded study from the San Francisco Bay Area, a study of Superfund Cleanup sites in Minnesota, and a study of children living in proximity to mercury-emitting coal fired power plants in Texas.
ENDOCRINE DISRUPTORS - These ubiquitous chemicals and other "early life immune insults," or ELIIs, "are important factors in childhood and adult chronic diseases," says one study from Cornell University. "However, prenatal and perinatal environmentally induced immune alterations have yet to be considered in depth in the context of autism and autism spectrum disorders."
PESTICIDES - One study presented at the 2008 International Meeting for Autism Research in London reported that mothers who used pesticide-based shampoos on pets doubled the risk of having an ASD child, compared to mothers who did not. Another study in the agriculturally intensive Central Valley of California reported that autism risk increased "with the poundage of organochlorine pesticides applied, and decreased with distance from field sites."
MERCURY IN FISH - At least one tiny study, from Australia, showed elevated mercury levels in three infants weaned on congee (a rice and fish porridge) and fed fish regularly as toddlers. Their parents had sought medical advice for developmental delay and neurological symptoms, including symptoms of autism spectrum disorder.
RETROVIRUSES - In October, researchers from the University of Nevada, the National Cancer Institute and The Cleveland Clinic announced the startling discovery of antibodies to a little known retrovirus in 95 percent of patients with Chronic Fatigue Syndrome. One of the researchers reported finding the same pathogen in 40 percent of autsim children tested. The work has been disputed by other scientists.
PREMATURE BIRTH AND EARLY BIRTH WEIGHT - Between 1990 and 2000, late preterm births in the US increased by 13 percent, and the rate of low birth-weight babies increased by 24 percent. Toxicologists calculate exposure rates to toxins based on kilograms of body weight.
VACCINES AND UNDERLYING DISORDERS - In January of this year, the Institute of Medicine's Committee to Review Adverse Effects of Vaccines issued its "Working list of adverse events to be considered." Included in the adverse events associated with the DTaP and MMR vaccines were "autism" and "Autism Spectrum Disorders (ASD)/Pervasive Developmental Disorders (PDD)." Interestingly, the IOM Committee said it would consider investigating so-called "Secondary" autism, or "autistic features arising from chronic encephalopathy, mitochondrial disorders and/or other underlying disorders." In other words, vaccines don't cause autism, but they might cause brain disease in certain predisposed kids, and that might lead to autism.
VACCINES AND IMMUNE STRESS - As for "Primary" autism, the IOM has been asked by the Federal Vaccine Injury Compensation Program (VICP, or Vaccine Court) to consider reviewing all the medical literature since the 2004 IOM report that found no link. "In particular, VICP is interested in the Committee's review on more recent theories of 'neuroinflammation' and 'hyperarousal/overexcitation of the immune system via multiple simultaneous antigenic stimulation." In other words, getting too many shots at once might cause an inappropriate neuro-immune response, such as that sometimes reported in autism.
VACCINES AND VIRAL PARTICLES - A brand new study reported finding pig and monkey viral particles in a number of vaccines. In the MMR II and Varivax (Chicken Pox) vaccines, researchers detected human endogenous retrovirus K, or HERV-K. The retrovirus was a "consequence of their manufacture using human cell lines." A 2001 study of genes and autism reports on the development of "frozen blocks of DNA" caused by imperfect gene duplication. "It appears that human endogenous retroviruses (HERV) and
HERV fragments are involved," the authors wrote. "The long version of the C4 gene, for
example, results from the integration of an HERV-K."
Do vaccines and vaccine ingredients belong on the list of candidates? Many people say no, but the IOM and the VICP say yes.
I agree with the experts. And now that we have a "changepoint" of 1988, we should go back and look at vaccine exposures both pre- and post- changepoint. Between 1988 and 1996, the following vaccines were added to the US schedule for children in the first 15 months of life:
- HiB - Improved Hib conjugate vaccine licensed in December 1987, and single dose added to childhood schedule in 1988.
- DTaP - Additional dose at younger age added around 1990.
- HiB - Three additional doses added to schedule in 1991.
- Hep B - Three doses - Added to childhood schedule in 1992.
- Chicken Pox - Approved in 1995, added to schedule in 1996
1988 was a very interesting year, and those children have a lot to tell us. Let's listen.
David Kirby is author of Evidence of Harm - Mercury in Vaccines and the Autism Epidemic and, most recently, Animal Factory: The Looming Threat of Industrial Pig, Dairy and Poultry Farms to Humans and the Environment - Both from St.. Martin's Press