A landmark study has determined that the older a man is when he has a child, the greater the risk of passing on genetic mutations that can cause autism and schizophrenia.
The Globe and Mail says researchers examined the genomes of 78 families in Iceland with children diagnosed with autism or schizophrenia and found that the father's age is crucial to the risk of a child developing one of the disorders.
The New York Times reports the study backs up the argument that the increasing rate of autism over the past few decades is related to the increasing age of fathers, and suggests that factor alone could account for 20 to 30 percent of cases.
The study published in Nature quotes lead author Kári Stefánsson, chief executive of deCODE Genetics in Reykjavik, saying,“The older we are as fathers, the more likely we will pass on our mutations.” “The more mutations we pass on, the more likely that one of them is going to be deleterious.”
Stefansson is quoted in the Globe and Mail saying, “Conventional wisdom has been to blame developmental disorders of children on the age of mothers,(but) our results all point to the possibility that as a man ages, the number of hereditary mutations in his sperm increases.”
The Globe and Mail says the study found that for every year of increase in a father's age, an average of two additional new gene mutations are passed on. That would mean that the number of new mutations passed on by dads would double every 16.5 years from the onset of puberty. And Nature reports that would mean that a 36-year-old man would pass on twice as many mutations to his offspring than a man of 20, and a father at the age of 70 would pass on eight times as many genetic mutations.
The New York Times says we have known for many years that the risk of chromosomal abnormalities, like Down syndrome, increases for older mothers, but when it comes to developmental and psychiatric disorders it now appears that the risk originates in the sperm and not the egg.
But The Times says experts caution that the research is not enough for men to forgo fatherhood later in life. They say the overall risk for a man in his 40s or older is still only about 2-percent at most, and there are other contributing factors that are still unknown. The US Centers for Disease Control and Prevention estimates 1-in-88 children is diagnosed with autism.
Darren Griffin, a professor of genetics at the University of Kent not involved in the study, is quoted in The Globe and Mail saying, the age finding is significant “but not one necessarily to cause great worry among prospective older fathers.” “There are three billion letters in the DNA code of humans and the numbers of mutations detected in this study are in the dozens.”
The Globe and Mail reports the results back up three American studies published in April, that found that genetic mutations could happen spontaneously in the egg or sperm cells, that increased the risk of autism. Those studies found that fathers were four times more likely to pass on the genetic mutations than mothers.
The Daily Mail suggests men are being told to consider freezing their sperm when they are younger to avoid the deterioration in genetic risk. The paper quotes Alexey Kondrashov, a professor of evolutionary biology at Michigan University, saying that if the findings are confirmed, "collecting the sperm of young adult men and cool-storing it for later use could be a wise individual decision."
And the New York Times says University of Washington genome professor Evan E. Eichler, suggests, "You have to understand that the vast majority of these mutations have no consequences, and that there are tons of guys in their 50s who have healthy children.”