Top 3 Reasons to Stop Fretting About Being an Old Dad

You probably heard about last week’s Nature study on older dads and autism; it got a lot of attention. The basic findings were fascinating but, in my opinion, far less sensational than what most of the news articles would have us believe.The researchers, led by Kári Stefánsson of deCODE Genetics in Iceland, showed that the average 20-year-old man passes on about 25 new single-letter DNA mutations to his child. (These kinds of mutations happen spontaneously in sperm cells, so they don’t affect the DNA in the father’s other cells.) With each passing year of age, the man’s sperm acquires two more mutations. This makes sense, biologically. Primordial sperm cells divide over and over throughout a man’s life. To use an over-used metaphor: Each time the code gets copied, it creates an opportunity for a spelling mistake. Primordial eggs, in contrast, go through far fewer divisions. Women, no matter what their age, pass on about 14 mutations to each child, the study found.The researchers also showed, using demographic data of Icelanders going back to 1650, that the average age of fathers has recently shot up, from 27.9 years in 1980 to 33 in 2011. Based on their calculations, that means the average number of mutations passed on to each kid (from mother and father combined) went from 59.7 to 69.9.Here’s the sensational part. Stefánsson says, given that these mutations have been linked to autism, the increase in older fathers could partially explain whyautism rates have risen over approximately the same time period. This is a plausible idea, sure, in theory. But there’s actually not much data to back it up (more on that later). And yet the assertion — reported in the New York Times, Wall Street Journal, Washington Post and more than 250 other outlets (Slate’s XXfactor blog even ran a piece titled, “Dude, Bank Your Sperm. It’ll Get You Laid.”) — was enough to scare some potential fathers. As one of my friends Tweeted, “great, my 34yr-old gonads may be ticking neuro-disorder timebombs.”It’s an unsettling feeling, I’m sure. I’ve felt a similar panic about being an older mother (though for different reasons). But honestly, men, of all the things to spend time worrying about, this study is not one of them. Here’s why.Read more at...The Last Word on Nothing, August 2012.