DNA passed on through generations

Men who have children at an older age are at a higher risk of having grandchildren with autism compared to younger grandfathers, according to new research.

Collaborating with researchers from King’s College London’s Institute of Psychiatry and the Karolinska Institute in Sweden, QBI’s Professor John McGrath has shown that risk factors for autism may accumulate over generations.

The study found that the risk of autism in the grandchild increased with older paternal age.

Compared to men who had children when they were 20–24, men who had a daughter when they were 50 or older were 1.79 times more likely to have a grandchild with autism and those who had a son were 1.67 times more likely to have a grandchild with autism.

About one child in 160 is diagnosed with autism in Australia, with boys affected four times more than girls.

Autism Spectrum Disorder (ASD) affects people in very different ways: some are able to live relatively normal lives, while others will require a lifetime of specialist support.

People with ASD find it challenging to communicate with and relate to others, and making sense of the world around them is often difficult. 

Recent reports have suggested that the prevalence of ASD may be increasing internationally.

Autism is caused by a combination of genetic and environmental factors. 

Previous studies have shown that older paternal age is also a risk factor for autism in children: the risk is more than doubled in fathers aged 50 or older.

The mechanism behind this link is unknown but may be explained by mutations in the male sperm cells. Sperm cells divide over time, and on each division new mutations may be introduced.

Genetic mutations are common and do not always result in the child developing autism.

The new findings suggest that these ‘silent’ mutations are passed on to the otherwise healthy child, but may influence the risk of future generations developing autism.

It may be that genetic risk accumulates over generations or there may be a threshold of risk factors, and until the threshold is reached the disorder does not manifest.