The risk of developing autism may be passed on through – and not just to – future generations, researchers say. The international study suggests older fathers are more likely to have grandchildren with autism than their younger counterparts. The mechanism is unclear but it is thought they may transmit “silent mutations” to their grandchildren. But experts have urged caution, stressing autism is the result of many different factors. The study, looking at almost 6,000 people with the condition, is published in the journal Jama Psychiatry. According to the National Autistic Society, more than one in every 100 people in the UK have the condition. Previous studies suggested older fathers may be at greater risk of having children with autism than younger dads. But the team of UK, Swedish and Australian researchers say this is one of the first pieces of evidence to show the risk can be passed on through – rather than just straight to – future generations. The “silent mutations” – changes in genetic material – are likely to have no obvious impact on older fathers’ own children, but they may build up through subsequent generations, or interact with other genes and environmental factors, to increase the chance of their grandchildren developing the condition, the researchers say. Using national databases from Sweden they studied almost 6,000 people diagnosed with the condition and more than 30,000 without, tracking their parents’ and grandparents’ ages. They found men who had a daughter when aged 50 or older were 1.79 times more likely to have a grandchild with autism, compared to men who fathered children when aged between 20-24. And those who had a son when 50 years of age or older were 1.67 times more likely to have a grandchild with the condition.
