when doing the right thing could backfire…
A new study links autism to genetic defects passed on by older parents rather than environmental factors.
If you've been watching the news, you might be aware of a recent study that found something a bit odd in and around Los Angeles and San Francisco, CA. Children born primarily to educated and well off parents in a few suburban areas of these cities are over 70% more likely to be diagnosed with an autism spectrum disorder than elsewhere in the state according to a review of some 2.4 million birth and medical records. Now that's a little odd, wouldn't you say? There are several hypothetical explanations, including a purely diagnostic one by the study's authors and environmental triggers aren't being ruled out, but there's no smoking gun that points to any certain cause. Or is there? An independent study could provide a nudge towards a possible answer.
Think about this for a moment. We have parents of autistic children who are highly educated and well off. Just as the researchers who found the affected clusters suggest, they would be very likely to notice the signs early on and take their children to a specialist. Considering that autism spectrum disorders are loosely defined and notoriously hard to pin down, there's a huge potential for over-diagnosing them, something that was pointed out by several doctors trying to work out why there's been such a sharp increase in autism diagnoses over the last decade. The tricky issue of identifying cases of autism combined with concerned parents who will ask for doctors' opinions should their children miss a certain developmental milestone could account for some of the elevated diagnoses. This is the diagnostic hypothesis by the authors of the study. However, it admittedly falls far short of explaining the sky high numbers of diagnosed cases.
But there's another thing that highly educated parents of autistic children seem to share and that's their age at pregnancy. Advanced degrees take time to complete and their well off recipients tend to postpone having kids until they stabilize financially and establish their careers. That's when nature might just have a sadistic laugh at their smart and cautious planning in the same way we would imagine a villain cackling before pressing the big red doomsday button, and increases their risk of having children with autism spectrum disorders.
In fact, one review of CDC statistics from populations in California shows that a ten year delay in motherhood can be linked to a disconcerting 38% increase in the odds of having an autistic child. Fathers didn't fare much better. The same ten year delay for men gives a 22% increase in the odds of fathering an autistic child. How exactly the process works is going to be require further study, but since we know that older parents can pass on more genetic defects to their children, this could be a plausible explanation for what's going on with rates of autism among well educated and affluent populations.
While putting off parenthood can be a wise idea in today's world, our bodies didn't evolve to do what's fiscally responsible in a post Industrial Revolution world in which people are routinely living into their 70s and having kids into their mid-30s and beyond. So if autism is somehow triggered by genetic problems in the germ cells of older parents, we would expect a rise in its incidence as the average age to start a family creeps upwards thanks to better food, medicine and our work patterns. Of course at this point, this is ongoing research and it will take a while and a lot of studies to tell whether this is really what's happening.
See: Grether JK, Anderson MC, Croen LA, Smith D, & Windham GC (2009). Risk of autism and increasing maternal and paternal age in a large north American population. American journal of epidemiology, 170 (9), 1118–26 PMID: 19783586
