Older fathers and autism

Kat - It's time to take a look at the top stories from this month with science writer Nell Barrie. Writer. So, there's really been one big story in the news this month and this is about older fathers. What's this one about?

Nell - So, this was looking at the number of mutations that old fathers tend to pass on to their children and specifically focusing on how that might increase the risk of having children with autism.

Kat - Because the headlines were really dramatic. They were saying, "Old dads causing autism and schizophrenia" and it was enough to really worry all my older male friends. What have they actually done in this study?

Nell - So, they were looking at how many new mutations fathers pass on to their children. So, that's mutations that arise in the sperm, not mutations that the father has himself. And what they found out by looking at a whole group of different families and comparing the genes. They looked at 78 groups comprising the mother, the father, and the child. So they were figuring out what mutations in the child weren't present in the mum or the dad, and where those mutations have come from. And they've discovered that the older father, the more new mutations he'll pass on to the child that have popped up in his sperm.

Kat - And in these children, they were more likely to have these conditions.

Nell - Yes, exactly. So, it looked at autism and schizophrenia and found out that children with more of these new mutations were more likely to have those conditions.

Kat - So, what does that this actually mean because on the surface, this is like, "Oh my God! All these mutations are causing autism" and older dads maybe - should they not have kids?

Nell - I think probably the main thing to bear in mind is that autism is a really, really complicated condition. So it's certainly not a case of saying, "You've got this gene. Therefore, you have autism." It just does not work like that. We know that it's quite heritable, meaning that in families where there's lots of autism you can see it passing through the generations, but that doesn't mean that that explains all of it. We also know that it seems to be becoming more common and people aren't quite sure why that is. So, I think a lot of the kind of hype around this was maybe that perhaps this explains why more children have autism now because dads tend to be older. But it's not that simple. It's not that easy to make that connection based on this research. We don't quite know enough yet, but it's certainly very exciting to see that that could be a cause of this perhaps.

Kat - Because I remember a couple of months ago in the Naked Genetics podcast, we covered a story just discussing that they'd discovered a whole bunch more of potential mutations that were involved in autism, and I think it's an incredibly complex disease. But it's also interesting about - there's a nice little vignette about the way that fathers' ages have changed in Iceland because probably round about the early 1900s, the average age from a dad was about 35 in Iceland and that dropped to under 30 during the 20th century, and then it's gone back up to 33. So in fact, fathers were older. I don't know if that means that the rates of autism have changed. It's very hard because we diagnose it differently now.

Nell - Yeah, it is really difficult because I mean, a lot of the research has made people think that perhaps some of the rise is due to just people knowing more about autism. So, children are more likely to be diagnosed because doctors are kind of looking for it. They're more aware and this is sort of perhaps arguing that maybe some of it is real, maybe it's to do with older dads, but we don't know about those patterns further back in time. So, it's not very clear what the sort of the changes could have been and I think it's quite interesting just thinking about it from a kind of social point of view I guess as well because we tend to see families being a little bit older when they have kids now, but that might change in the future. And it's to do with the way people think about how they plan their lives, their jobs, all that kind of thing. So, it's an interesting kind of crossover between genetics and looking at a whole much bigger area as well.

Kat - They were saying, "Maybe men should bank their sperm." You know, bank your sperm in your early 20s and then get it back out of the freezer again if you want to be a dad. But I think one of the really interesting things to think about is what does this mean for us as a species because obviously, mutations are good. They're what drive the natural variation in populations and this is what drives evolution and an awful lot of mutations are just neutral. They're not bad and they're not good. Obviously, some mutations are good. So maybe this increased rate of mutations in dads could be a good thing, do you reckon?

Nell - Absolutely, yeah and I think - I mean, there were some commentary about this saying, "Oh well, yeah, doom and gloom." This could just mean that our genes are getting progressively worse as mothers and fathers get older over time. And I sort of thought, "Well, it's all relative because the mutations that you have are only bad or good, depending on the environment that you're in." So, as our environments changes, the way people live their lives change, you don't know what's a bad or a good mutation, and it's all kind of how you use it I guess.

Kat - Well it's certainly really interesting developments in what's an on-going and quite complicated story. So, thanks very much for chatting about it, Nell. That's Nell Barrie, Science Writer.