The largest-ever multinational study of parental age and autism risk found increased autism rates among the children of teen moms and among children whose parents have relatively large gaps between their ages. The study also 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.
The study, funded by Autism Speaks, appears online today in the journal Molecular Psychiatry.
Specifically the study found:
* Autism rates were 66 percent 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 18 percent higher among children born to teen moms than among those born to moms in their 20s.
* Autism rates were 15 percent higher in children born to mothers in their 40s, compared to 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 years old and their partners were 10 or more years younger. Conversely, rates rose when moms were in their 30s and their partners were 10 or more years younger.
The higher risk associated with fathers over 50 is consistent with the idea that genetic mutations in sperm increase with a man’s age and that these mutations can contribute to the development of autism. By contrast, the risk factors associated with a mother’s age remain unexplained, as do those associated with a wide gap between a mother and father’s age.