LONDON - A father's age, not a mother's, when a baby is conceived is the single largest factor in the risk of passing on new gene mutations to children and may help explain why childhood autism rates are rising, scientists said on Wednesday.
In a study which turns conventional thinking on its head, researchers sequenced the genomes of 78 Icelandic families with children diagnosed with autism or schizophrenia and found a father's age was crucial to the genetic risk of such disorders.
"Conventional wisdom has been to blame developmental disorders of children on the age of mothers," said Kari Stefansson, chief executive of the private firm deCODE Genetics in Reykjavik, whose work was published in the journal Nature.
"(But) our results all point to the possibility that as a man ages, the number of hereditary mutations in his sperm increases."
He said this age-linked increase in mutations proportionally increased the chance a child might carry a harmful mutation that could lead to conditions like autism and schizophrenia.