Published on March 21st, 2013 | by James Ayre0
Men Who Have Children Later In Life More Likely To Have Autistic Grandchildren, Risk Factors For Autism Accumulate Over Generations
It was already known that men who father children later in their life are much more likely to have autistic children than younger men, but new research has found that this effect extends to their grandchildren also. This new research shows that risk factors for autism can accumulate over generations, much in the same way as radiation damage and chemical exposure can.
The new findings are the result of a collaboration between King’s College London’s Institute of Psychiatry, Karolinska Institutet in Sweden and the Queensland Brain Institute in Australia.
“By using Swedish national registers, researchers identified 5,936 individuals with autism and 30,923 healthy controls born in Sweden since 1932. They had complete data on each individual’s maternal and paternal grandfathers’ age of reproduction and details of any psychiatric diagnosis.”
It was found “that the risk of autism in the grandchild increased the older the age of the grandfather at the time his son or daughter was born. Men who had a daughter when they were 50 or older were 1.79 times more likely to have a grandchild with autism. Men who had a son when they were 50 or older were 1.67 times more likely to have a grandchild with autism, compared to men who had children when they were 20-24.”
It’s a very interesting finding. Ideas similar to this have been circulating in recent years, but there hasn’t been much research done yet to test them. The last century has seen an explosion in the number of children born with developmental disorders, and other diseases for that matter. There has been some debate about whether, with regards to autism, it is simply being diagnosed more often, or whether it is the result of the vast environmental changes that humans have caused over the past few hundred years. Recent research has shown that exposure to many commonly used chemicals, such as many pesticides, can cause changes that are passed down through multiple generations, having a cumulative effect. Radiation exposure, especially to the reproductive system, works similarly, in a cumulative way.
Dr Avi Reichenberg, from King’s Institute of Psychiatry and co-author of the paper says: “We tend to think in terms of the here and now when we talk about the effect of the environment on our genome. For the first time in psychiatry, we show that your father’s and grandfather’s lifestyle choices can affect you. This doesn’t mean that you shouldn’t have children if your father was old when he had you, because whilst the risk is increased, it is still small. However, the findings are important in understanding the complex way in which autism develops.”
Emma Frans, lead author of the study from Karolinska Institutet says: “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.”
Autism has been a growing problem in recent years, the number of people diagnosed with it has been rising at a significant rate. The exact causes have been completely clear, but the evidence points towards a mixture of genetic and environmental factors. “Previous studies have shown that older paternal age is a risk factor for autism in children: fathers aged 50 or older have a more than doubled risk to have a child diagnosed with autism compared to younger fathers.”
“The mechanism behind this link is unknown, but may be explained by mutations occurring in the male sperm cells. Sperm cells divide over time, and on each division the genome is faced by the possibility of new mutations being introduced.”
“However, most genetic mutations do not 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. The authors suggest that genetic risk could accumulate over generations, or could interact with other risk factors, until it reaches a threshold resulting in the disorder manifesting itself.”
Not a truly surprising finding, many of the most convincing objections against the use of certain chemicals, or increased radiation exposure (airport security), have brought up similar points. Just because “low-level” radiation or chemical exposure doesn’t produce immediately clear changes in an organism doesn’t mean that changes aren’t occurring in its genome, or that these changes won’t cumulatively cause a problem in future generations.
And it’s very important to note that people are largely no longer subject to the “natural” selection that works in most organisms to pare back a species to its healthiest members, eliminating those that are most prone to poor health or disfunction. Having a healthy immune system, a clever mind, and a body capable of obtaining it’s own food, aren’t even requirements anymore in this world of antibiotics, industrial agriculture, guns, vaccines, cesarean sections, and modern transportation.
Image Credit: Four Generations via Shutterstock