While older moms are usually the cause of genetic diseases in their children such as Down’s Syndrome, a new study in the journal Nature suggests that it is older fathers responsible for the rise in autism.
The study was done in Iceland in 78 families who had a diagnosis of autism or schizophrenia. The sequences of their genes were compared to those of 1859 Icelanders from the general population.
The researchers found that fathers older at conception were four times more likely to pass on new mutations as older mothers. While most of these mutations are harmless, some are the ones associated with autism and schizophrenia. It doesn’t prove an absolute cause, but it does seem a significant contribution to the rising numbers of autistic children.
For example, a 20-year-old dad passes on average 25 new genetic mutation errors to his child; a 50-year-old passes on about 65.
This is an important part of counseling older couples and will likely increase the risks we discuss when women consider egg donation and fertility counseling and family building in general.