To better understand the cause of new hereditary mutations, the deCODE team sequenced the genomes of 78 Icelandic families with offspring who had a diagnosis of autism or schizophrenia. The team also sequenced the genomes of an additional 1,859 Icelanders, providing a larger comparative population.
On average, the investigators found a two mutation per-year increase in offspring with each one-year increase in age of the father. The average age of the father in the study was 29.7 years old. Also, when specifically examining the genomes of families with autism and schizophrenia, the authors identified in offspring mutations in genes previously implicated in the diseases. They also identified two genes, CUL3 and EPHB2, with mutations in an autism patient subgroup.
Epidemiological studies in Iceland show the risk of both schizophrenia and autism spectrum disorders increases significantly with father’s age at conception, and that the average age of father’s in Iceland (now 33 years-old) at the time a child is conceived is on the rise. The authors noted that demographic change of this kind and magnitude is not unique to Iceland, and it raises the question of whether the reported increase in autism spectrum disorder diagnosis is at least partially due to an increase in the average age of fathers at conception.