The mutations that men accumulate in their sperm as they age don’t account for most of their increased risk of having a child with autism, reports a study published today in Nature Genetics1. Instead, the researchers suggest, men who carry risk factors for the condition simply tend to have children late in life.
Several large epidemiological studies from the past decade suggest that the older a man is when he has a child, the more likely he is to have a child with autism or schizophrenia. For example, one study reported that men aged 50 years and older are twice as likely as men under age 30 to have a child with autism. At the same time, sequencing studies suggest that each year a man ages, he passes an estimated two more de novo, or spontaneous, mutations to children he sires.
The findings suggest that de novo mutations in sperm account for, at most, 20 percent of the increased autism and schizophrenia risk associated with the father’s advanced age. “The small number of additional mutations in children with older fathers can’t really explain the increase in risk that we see,” Gratten says.
