According to new research published in JAMA Psychiatry, older men who have children are more likely to have grandchildren with autism compared to men who have children at a younger age.
The research indicates that risk factors for autism build up over generations.
The study was carried out by researchers from the Karolinska Institutet, King’s College London’s Institute of Pschiatry (IoP), and Queeensland Brain Institute.
They analyzed Swedish national registers and looked at the maternal and paternal backgrounds of 5,932 people with autism as well as 30,923 healthy controls. They gathered information about any psychiatric diagnosis and the grandfathers’ age of reproduction.
The results of the study indicate that there’s an association between the age of male reproduction and increased risk of autism in his grandchildren. Compared to men who had children between the ages 20 to 24, men above the age of 50 who had a daughter were 1.79 times more likely to have an autistic grandchild, those who had a son were 1.67 times more likely.
The lead author of the study, Emma Frans, from Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics, said:
“We know from previous studies that older paternal age is a risk factor for autism. This study goes beyond that and suggests that older grandpaternal age is also a risk factor for autism, suggesting that risk factors for autism can build up through generations.”
One percent of the Swedish population has an autism spectrum disorder (ASD), with more men being affected than women. Some people with the disorder are able to live relatively everyday lives, however, the condition can affect people in different ways and some require a lifetime of specialist support.
People with an ASD have trouble understanding the world around them, most have problems with non-verbal communication, a wide-range of social interactions, and activities that include an element of play and/or banter.
Autism is caused by both genetic and environmental factors. Previous studies have suggested that paternal age can be a risk factor for autism. Some experts believe this is due to mutations occurring in male sperm cells over time, as each as sperm cell divides there is a chance of mutation.
Most of these genetic mutations don’t affect the child but can increase the risk of future generations having autism. The researchers believe that the genetic risk builds up over time, along with other risk factors, to a point that the disorders begin to develop.
Researchers at the Seaver Autism Center at Icahn School of Medicine at Mount Sinai explained how new genomic technology has allowed scientists to further understand autism. The new technology, called HTS (high-throughput sequencing), has enabled scientists to obtain the sequence of all 22,000 human genes. It has shown that there are not just a few mutations, but possibly hundreds of mutations linked to autism.
The Swedish Research Council, Karolinska Institutet, and the Swedish Council for Working Life and Social Research (FAS) financed the study.
The Centers for Disease Control and Prevention announced earlier this week that as of 2012, one in every 50 children aged 60 to 17 in the USA has an autism spectrum disorder. Five years previously, the ratio was 1 in 88. Stephen Blumberg, a senior scientist at the CDC’s National Center for Health Statistics, said “This estimate was a bit surprising. There may be more children with autism spectrum disorder than previously thought.”
Written by Joseph Nordqvist