"The UK and US researchers examined data on 132,271 children and said those born to men over 40 were six times more at risk than those born to men under 30. "
"Older parental age has previously been linked to abnormalities in the brain development of children. "
"Among those whose fathers were between 15 and 29 when they were born, the rate of autism was six in every 10,000, rising to nine in every 10,000 when fathers were aged 30 to 39 (1.6 times higher).
In the group whose fathers were aged 40 to 49, the rate rose to 32 in 10,000 (5.75 times higher).
The rate appeared to be even higher when fathers were aged over 50, but the researchers said the sample size was very small.
The mother's age did not appear to influence the chances a child would have autism.
The researchers suggest there may be a genetic fault which is more common with age. "