(Photo : Creative Commons/Erik Derr)
Men who have children when they are older have a greater chance of having grandchildren with autism, says a new study that suggests risk factors for autism may build up over generations.
The research, led by a team at the Institute of Psychiatry at King's College London, determined men who had a daughter when they were 50 years or older were 1.79 times more likely to have a grandchild with autism than men between the ages of 20 and 24.
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With sons the chances rose 1.67 times.
The study, published March 20 in the Journal of the American Medical Association's "JAMA Psychiatry," used Swedish national registers and analyzed data from 5,936 people with autism and 30,923 healthy subjects born in Sweden since 1932.
The researchers from Britain, Sweden and Australia considered each person's maternal and paternal grandfathers' age of reproduction and details of any psychiatric diagnosis.
Avi Reichenberg, who co-led the study, said the work demonstrates that the lifestyle choices one makes can indeed be felt generations afterward.
He did add, though, "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."
Caused through a combination of genetic and environmental factors, autism disorders may range from severe mental disability and a profound inability to communicate to comparatively mild symptoms.
Some with autism, such as those diagnosed with Asperger's syndrome, may in fact function at high levels
A new survey suggests 1 in 50 children In the United States suffer some degree of autism.
"We know from previous studies that older paternal age is a risk factor for autism," said Emma Frans from the Karolinska Institute in Sweden, another of the study's co-leaders. "This study goes beyond that and suggests that older grand-paternal age is also a risk factor for autism, suggesting that risk factors for autism can build up through generations."
The researchers said that while the exact reasons for autism's link to older fathers and grandfathers is not clear, it may be explained by mutations occurring in sperm cells over time.