Children born to older dads run a higher risk of having autism, psychiatric disorders and performing badly at school, researchers have warned.
They found children conceived when fathers were 45 and older were on average three and a half times more likely to have autistic problems compared with the offspring of men in their early 20s.
The risk was even higher at 24-fold for bipolar disorder and 13-fold higher for ADHD, says a report in JAMA Psychiatry journal.
Researchers warned that advancing paternal age posed a risk of ‘numerous public health and societal problems’.
They said men should be advised about the potential problems in order to help their personal decision-making when it came to having fathering children at older ages.
Among well-known older dads are Simon Cowell, 54, whose son was born earlier this month, and comedian Frank Skinner whose first child was born in 2012 when he was 55.
Mounting research suggests the older age of parents might be partly responsible for growing numbers of children with autism.
Autism is an umbrella term for a range of developmental disorders that have a lifelong effect on someone’s ability to interact socially and communicate.
In the UK, around one in 100 adults is thought to be affected by autism, mostly men, caused by a combination of genetic and environmental factors.
Experts think the link with paternal age could be explained by genetic errors creeping into sperm production as men get older, which build up over time.
In the latest study, researchers studied people born in Sweden from 1973 to 2001 and estimated the risk of psychiatric problems such as autism, bipolar disorder and attention deficit hyperactivity disorder, and academic trouble.
The study used several models to establish estimates of risk depending on the father’s age, including comparisons of siblings, cousins and first-born cousins.
It concluded there was a 3.5 fold higher risk of autism among children of fathers aged 45 and over, compared with dads aged 20 to 24 years old.
Those born to older fathers had a 13-fold extra risk of ADHD, 24-fold higher risk of bipolar disorder, and double the risk of suicide attempts and substance abuse.
There was also a higher risk of academic problems such as failing a grade and low attainment.
Researcher Brian D’Onofrio, of Indiana University, Indiana, U.S., said: ‘Advancing paternal age is associated with an increased risk of psychiatric and academic morbidity, with the magnitude to risks being as large, or larger, than previous estimates.’
Dr D’Onofrio added: ‘We were shocked by the findings.
‘The specific associations with paternal age were much, much larger than in previous studies. In fact, we found that advancing paternal age was associated with greater risk for several problems, such as ADHD, suicide attempts and substance use problems, whereas traditional research designs suggested advancing paternal age may have diminished the rate at which these problems occur.’
Previous studies have shown that fathers aged 50 and older are more than twice as likely to have a child diagnosed with autism than younger fathers, while some research suggests older mothers may also be more at risk.