For every few studies showing evidence that something leads to autism, there is always a study floating around with research disproving previous beliefs of possible ASD triggers. Recent research, stemming from Australia’s University of Queensland, focused on the long-studied idea of older fathers and their risk of giving birth to a child on the autism spectrum.
In the past decade, researchers have believed that men over the age of 50 that have children can increase the chance of having offspring with ASD due to mutations in their sperm that develop as they age. The study from The University of Queensland found that it’s more likely that men with any autism risk factors just end up conceiving late in their lives.
Two separate study conclusions were pushed together to form this belief. One study said that men over the age of 50 were two times more likely to have children with ASD than men under the age of 30. This coincided with the time that another study surfaced, saying that a man gains two random mutations, called de novo mutations, for every year he ages. These two conclusions were grouped together for the belief that older fathers increase the chance of autism.
The lead investigator of the newest study was James Gratten, a research fellow in neurogenetics and statistical genomics at the University of Queensland. He said that this belief was formed from assumptions of the two study conclusions.
“People have put two and two together and said that the extra mutations explain the increased risk in the children.” Gratten said.
Gratten and his team focused on mathematical models that incorporated multiple pieces of information such as the change of de novo rates with age, ASD and schizophrenia general rates, and how these are connected to hereditary and fertility effects.
With just 20 percent of the mutations linked to autism and schizophrenia from older male age, the researchers don’t find that the assumption holds too much water.
“The small number of additional mutations in children with older fathers can’t really explain the increase in risk that we see,” Gratten explains.
The models all figured that men between the ages of 35- to 39-years-old pass along 20 more mutations to their offspring than those in their 20s. Each model conveys different ideas of how strong de novo mutations have on ASD.
One of the main conclusions of the study is that older fathers actually contribute very little to the overall ASD rate. With the 20 percent of mutations leading to ASD, inherited factors contributing to about half of the risk, and ASD patients with children adding on another 35 percent chance, age-related mutations only account for 10 percent risk for older fathers.
For more information, check out the source for this blog post, Spectrum News.