Blaming Older Fathers for the "Autism Surge" Is Off the Mark
Mainstream media articles on autism science can be frustrating. In the race to woo eyeballs, writers too often spin research findings -- because readers who gasp at, then forward the post generate more page views than those who than try to understand what the represented research means. It's even more bothersome when a story with a sensationalistic headline has a caveat-bearing back end, as that's the part trigger-happy Tweeters and Tumblrs and etc. are less likely to read. I'm watching autism science ado happen online right now, as The New York Times' Father’s Age Is Linked to Risk of Autism and Schizophrenia and similar articles mobilize outcries about elderly sperm driving an "autism surge" -- even thought that's not really what the originating Nature article concludes.
It's easy to see how the opening paragraphs of the Nature piece sparked such hoopla:
By starting families in their thirties, forties and beyond, men could be increasing the chances that their children will develop autism, schizophrenia and other diseases often linked to new mutations. “The older we are as fathers, the more likely we will pass on our mutations,” says lead author Kári Stefánsson, chief executive of deCODE Genetics in Reykjavik. “The more mutations we pass on, the more likely that one of them is going to be deleterious.”
Those who freak out, stop reading, and start forwarding miss critical conclusions as to why these findings -- though grounded in legitimate science (unlike vaccine causation theories of autism) -- don't explain rising autism rates the way heritability does:
...Mark Daly, a geneticist at Massachusetts General Hospital in Boston who studies autism, says that increasing paternal age is unlikely to account for all of the rise in autism prevalence. He notes that autism is highly heritable, but that most cases are not caused by a single new mutation — so there must be predisposing factors that are inherited from parents but are distinct from the new mutations occurring in sperm.
It's also important to note a preferred explanation for increased autism rates: as scientist Emily Willingham writes at Discover Magazine's The Crux, autism is not new; we've just become better at identifying autistic people due to refined diagnostic criteria:
...here we are today, with two diagnoses [autism and Asperger's] that didn’t exist 70 years ago (plus a third, even newer one: PDD-NOS) even though the people with the conditions did. The CDC’s new data says that in the United States, 1 in 88 eight-year-olds fits the criteria for one of these three, up from 1 in 110 for its 2006 estimate. Is that change the result of an increase in some dastardly environmental “toxin,” as some argue? Or is it because of diagnostic changes and reassignments, as happened when autism left the schizophrenia umbrella?
I talked with Emily about the older fathers study, and she emphasized the points above -- the science behind older fathers handing down higher percentages of genetic mutations is solid, but any extrapolation pinning those percentages to increased autism rates does not acknowledge additional, more likely explanations. She also expressed irritation over headlines trumpeting an "autism surge" while failing to acknowledge the lack of a similar "surge" in schizophrenia rates.