Autism rates were more among the children of teen moms and among children whose parents have relatively large gaps between their ages, reports a recent multinational study finding.
The study confirmed that older parents are at higher risk of having children with autism. The analysis included more than 5.7 million children in five countries.
Co-author Michael Rosanoff said that by linking national health registries across five countries, they created the world's largest data set for research into autism's risk factors. The size allowed them to look at the relationship between parents' age and autism at a much higher resolution.
Co-author Sven Sandin added, "Although parental age is a risk factor for autism, it is important to remember that, overall, the majority of children born to older or younger parents would develop normally."
The study found that Autism rates were 66% higher among children born to dads over 50 years of age than among those born to dads in their 20s. Autism rates were 28 percent higher when dads were in their 40s versus 20s.
Autism rates were 15 percent higher in children born to mothers in their 40s, compared to those born to moms in their 20s and were 18 percent higher among children born to teen moms than among those born to moms in their 20s.
Autism rates rose still higher when both parents were older, in line with what one would expect if each parent's age contributed to risk. Autism rates also rose with widening gaps between two parents' ages.
These rates were highest when dads were between 35 and 44 and their partners were 10 or more years younger. Conversely, rates were high when moms were in their 30s and their partners were 10 or more years younger.