Parental age is a 'risk factor' for autism

A story today talks about how parental age _may_ be a ‘risk factor’ (loaded phrase much?) for autism. According to the studies lead author (Dr. Maureen Durkin of the University of Wisconsin School of Medicine and Public Health):

What we found was that actually it’s both parents age, and when you control for one parent’s age you still see the effect of the other parent’s age, and vice versa,

….

After the researchers accounted for factors that might influence the results, they found that children born to mothers aged 35 and older were 30 percent more likely than those whose mothers were 25 to 29 years old to have been diagnosed with autism. Having a father who was 40 or older boosted risk by 40 percent.

The study didn’t really look at why this might be but they did do a bit of educated blueskying:

Older parents have had a longer time to sustain genetic damage to their sperm or egg cells, as well as to store up environmental contaminants in their bodies.

They are also more likely to have used assisted reproduction technologies, which have been tied to poor pregnancy outcomes. And there could be something about the behavioral traits or psychological makeup of people who wait to have children that boosts autism risk in their offspring.

Which is all a fancy way of saying: I got nuthin’ so here’s an answer that covers everything. Which is fair enough, it falls totally outside the remit of the paper to answer those questions.

So now you can expect a whole bunch of people to cast aspersions on this study, relating how really they were only 19 when they had an autistic kid and that its all a big conspiracy to detract from the evil vaccines. Whatever.

Its quite an interesting study, the most recent of many that look at (and find a connection) between parental age and autism. Does it move us forward in terms of causation? Nope. Does that really matter? Nope. Its still nice though to see science being done that is just that most important of work – the hog work that starts to fill in the blanks of the most basic facts surrounding an issue. Thanks to this study and those preceding it I think its fair to say now that raised parental age is a factor in autism causation. Not always but sometimes.

Another interesting bit of blueskying:

The findings could also help explain why autism appears to be on the rise in the United States, the researchers added, since the percentage of children who are born to mothers 35 and older and fathers 40 and older has risen steadily since 1980.

I think this is a very interesting hypothesis to follow up on and I hope someone does. But first of all of course we need to establish _if_ autism is ‘on the rise’. Many people will tell you there’s an epidemic of autism but there is in fact no valid evidence to support this supposition. I hope some evidence can be forthcoming. We need it.