Older fathers may pass autism risk to grandchildren

Men who father children later in life are more likely to have grandchildren with autism, according to research.

Emma Frans from the Karolinska Institutet in Sweden, the lead author of the study, says the work suggests 'that risk factors for autism may accumulate over generations'.

In the study, 5,936 people with autism were identified using the Swedish national register. Researchers compared the age of these people's grandfathers with those of 30,923 healthy controls.

Men who had a daughter after the age of 50 were 79 percent more likely to have a grandchild with autism than younger (20 to 24 years old) fathers. If men had a son when aged 50 or over, the odds of a grandchild developing the condition increased by 67 percent.

'For the first time in psychiatry, we show that your father's and grandfather's lifestyle choices can affect you', said co-author Dr Avi Reichenberg, from King's Institute of Psychiatry in London.

However, the paper stresses that 'older men should not be discouraged to have children'. Although the risk of a grandchild developing autism increased for older fathers, it was still small, the researchers add.

Caroline Hattersley of the UK's National Autistic Society told the BBC: 'The study is not definitive as we know that many people who had children at a young age also have grandchildren with the condition. We therefore urge parents and those thinking of starting a family not to be concerned about the findings'.

Autism is thought to develop as a result of genetic and environmental factors and these are incompletely understood. Previous studies suggest that men who reproduce at older ages pass more genetic mutations to their children, some of which are linked to an increased risk of autism (see BioNews 670 and 652).

Autism spectrum disorders range from severe conditions where a person's communication is very limited, to milder forms such as Asperger's syndrome.

The National Autistic Society describes autism as a 'lifelong developmental disability that affects how a person communicates with, and relates to, other people'. It estimates that at least half a million people in the UK have autism. In the US, between one in 50 and one in 88 children are thought to have an autism spectrum disorder.