An older mum OR dad increases autism risk going against current perceptions

By
Jo Macfarlane

Last updated at 4:26 AM on 5th February 2012

Couples have a greater risk of having a child with autism if either the father or the mother is over the age of 35, according to a major international study.

The findings have come as a  surprise as it was previously thought that delaying motherhood represented the greatest risk.

But the new study found that if either parent is between 35 and 39  – regardless of whether it is the mother or the father – then the extra risk of having an autistic child is the same.

Older parents are now believed to increase the risk of autism in children

Older parents are now believed to increase the risk of autism in children

In both cases there is a 27 per cent greater chance of having a child on the autistic spectrum compared with families where both parents are under 35. But if both parents are in their late 30s, the risk does not increase any further than if only one of them is.

However, if one parent is under  35 and the other 40 or over, the extra risk of autism is greater with an older mother (65 per cent) compared with an older father (44 per cent).

Autism was thought to be linked to natural changes that occur to both eggs and sperm as people age.

The new study suggests that while age still plays a role, there must also be some other explanation which is not yet known.

The study examined 1.3 million children born in Denmark between January 1980 and December 2003 

The researchers said that they ‘could not rule out’ the effect of other environmental factors such  as infections, medication or fertility treatment, and added that more work was needed to see if this was the case.

But they also suggested their findings could reflect the fact that older parents may seek help for children with developmental delays sooner.

The study examined 1.3 million children born in Denmark between January 1980 and December 2003. Of those, 9,556 were later diagnosed with a disorder on the autistic spectrum by a child psychiatrist after being referred for treatment. This includes autism, Asperger’s syndrome and other developmental conditions.

The study, published in the journal Annals Of Epidemiology, was led by Professor Erik Thorlund Parner at the University of Aarhus in Denmark, but also included work by Professor Simon Baron-Cohen at Cambridge University.

The study examined 1.3million children born in Denmark between January 1980 and December 2003

The study examined 1.3million children born in Denmark between January 1980 and December 2003

Prof Parner said: ‘The [old] explanation was that new mutations in the sperm increase the risk for autism, and that new mutations in the egg increase the risk for autism.

‘One would then expect that if a couple had these particular mutations in both the sperm and the egg, then they would have a higher risk for autism than if only one parent had the particular mutation. We don’t see this pattern.’

Caroline Hattersley of The National Autistic Society said: ‘While this research suggests that there is a link between parental age and autism, more studies are needed to understand the factors.

‘Much research has posited risk factors, but we know little about the biological chain of events that gives rise to autism.’

Autistic spectrum disorders affect about one per cent of all children.  After that,  Ms Stewart, who is dating her Twilight co-star  Robert Pattinson, will be seen in a big-screen version of Jack Kerouac’s classic Beat Generation book On The Road and Snow White And The Huntsman, a reworking of the familiar fairy tale.

 

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