I’ve been thinking our environment lately, and so just couldn’t resist this post. I’m sure there is much I haven’t considered about autism, but the new book by Enriquez and Gullans struck a chord with me (see below).
The Mortality and Morbidity Weekly Report (MMWR) (like the Kelley Blue Book), provides, in mind-numbing detail, just how many people got sick or died last week. It’s not exactly beach reading, and it’s usually as exciting as watching paint dry. But within the endless columns and statistics of the MMWR, the patient and persistent can spot long-term trends and occasionally find serious short-term discontinuities. Autism is one of these discontinuities.
Conditions and diseases develop and spread at different rates. A rapid spike in airborne or waterborne infectious diseases like the flu or cholera is tragic but normal. A rapid spike in what was thought to be a genetic condition, like autism, is abnormal; when you see the latter, it is reasonable to think something has really changed, and not for the better.
Usually changes in the incidence of a genetically driven disease take place slowly, across generations. Diseases such as cystic fibrosis result from well-characterized DNA mutations in single genes, and the inheritance pattern is well understood: If parents carry the gene and pass it to a child, the child will be affected. Cystic fibrosis occurs in 1 of 3,700 newborns in the United States each year with no significant change in incidence over many years. You cannot ‘catch’ these kinds of conditions by sharing a room with someone; you inherit them. If your sibling has cystic fibrosis, then you have a 1 in 4 chance of also being sick.
Autism is diagnosed in 1 percent of individuals in Asia, Europe, and North America, and 2.6 percent of South Koreans. We know there is a strong genetic component to autism — so much so that until recently autism was thought to be a primarily genetic disease. There is clearly an underlying genetic component to many cases of autism. If one identical twin has autism, the probability that the other is also affected is around 70 percent. Until recently, the sibling of an autistic child, even though sharing many of the same parental genes and overall home environment, had only a 1 in 20 probability of being afflicted. Meanwhile, the neighbor’s child, genetically unrelated, has only a 0.6 percent probability. But even though millions of dollars have been spent trying to identify ‘the genes’ for autism, so far the picture is still murky. The hundreds of gene mutations identified in the past decade do not explain the majority of today’s cases. And while we searched for genes, a big epidemic was brewing:
|Surveillance year||Birth Year||Prevalence per 1000 children||This is about 1 in X children:|
|2000||1992||6.7||1 in 150|
|2002||1994||6.6||1 in 150|
|2004||1996||8.0||1 in 125|
|2006||1998||9.0||1 in 110|
|2008||2000||11.3||1 in 88|
|2010||2002||14.7||1 in 68|
In 2008, when the MMWR reported a 78 percent increase in autism — a noncontagious condition — occurring in fewer than eight years, alarm bells began to go off in the medical community. By 2010 the Centers for Disease Control and Prevention (CDC) was reporting a further 30 percent rise in autism in just two years. This is not the way traditional genetic diseases are supposed to act. This rate of change in autism was so shocking and unexpected that the first reaction of many MDs was that it wasn’t really that serious. Many argued, and some continue to argue, that we simply got better at diagnosing (and overdiagnosing) what was already there. But as case after case accumulates and overwhelms parents, school districts, and health-care systems, there is a growing sense that something is going horribly wrong, and no one really knows why.
What we do know, because of a May 2014 study that looked at more than 2 million children, is that environmental factors are driving more and more autism cases. These environmental factors can range from parental age at conception, maternal nutrition and infection during pregnancy – to exposure to certain chemicals such as pesticides and phthalates. Whereas autism used to be 80 to 90% explained or predicted by genetics, now genetics is only 50 percent predictive. Autism Speaks continues to fund research on a wide range of environmental risk factors that help us advance our understanding of these environmental risk factors.
It should be remembered that genetic risk factors coupled with environmental risk factors work hand in hand. It’s not an either/or scenario, but rather a complicated interaction of genetics and environmental factors, working together.
But the fact remains, we have taken a disease we mostly inherited and rapidly turned it into a disease we can trigger. Now the chances of a brother or sister of an autistic child developing autism is 1 in 8 instead of 1 in 20.
And yet. Human clinical trials for chemicals which might lead to autism would be unethical, and the variety and interactions of various chemicals is so extensive, it’s very hard to trace exactly which chemicals, in what combinations, alter the brain.
Juan Enriquez and Steve Gullans have published a new book, “Evolving Ourselves: How Unnatural Selection and Nonrandom Mutation are Changing Life on Earth”. (Who are they? Juan Enriquez was the founding director of the Life Sciences Project at the Harvard Business School and is a fellow at Harvard’s Center for International Affairs; Dr. Gullans was on the faculty of the Harvard Medical School and Brigham and Women’s Hospital for nearly 20 years. Both of them have a curriculum vitae as long as your arm if you care to look them up.) The premise of the book is that we humans hold, in our not always careful hands, the future of life on Earth: they argue that we have discarded random mutation and natural selection for their opposites: i.e., nonrandom mutation and unnatural (i.e., human) selection. (If you want to read more it’s easy to google the title and buy on Amazon – which is what I did.)
Reading the book, I was struck by a chapter that discussed autism. Andrey Rzhetsky, director of the Conte Center for Computational Neuropsychiatric Genomics at the University of Chicago, believes there is enough data to define the causes of autism – so he queried 100 million medical records trying to figure out the best correlations between environmental changes and autism. Bit of backstory: boys are acting like the proverbial canary in a coal mine. They are especially vulnerable to environmental insults from the chemicals that surround us. “Autism appears to be strongly correlated with rate of congenital malformations of the genitals in males across the country. This gives an indicator of environmental load and the effect is surprisingly strong.” Every 1% increase in malformations corresponded to a 283% increase in autism in the same county. In fact, the book says that Mr. Rzhetsky sees autism as a sort of chemical poisoning.
Naturally, not everyone agrees with Rzhetsky. And we don’t dare point fingers to any particular chemical – but shouldn’t we at least ask our government to restrict the use of some of the chemicals which are known to adversely impact human health? Ask your congressman to support the Safe Chemicals Act of 2013.
 Sandin, Sven, Lichtenstein, Paul, et al., “The Familial Risk of Autism”, Journal of the American Medical Association (JAMA), 2014; 311(17):1770-1777
 Sifferlin, Alexandra, “Growing Evidence that Autism is Linked to Pollution”, Time, March 14, 2014
 op cit.