August 23, 2012
Children Of Older Dads Have An Increased Risk Of Autism And Schizophrenia
Connie K. Ho for redOrbit.com — Your Universe OnlineBloomberg Businessweek, it is the first report by scientists that quantifies the effect of the disorders. The findings were published recently in the online edition of the journal Nature and support the belief that an increase in the rates of autism can be partly attributed to the older average age of fathers.
“The older we are as fathers, the more likely we will pass on our mutations,” explained lead author KÃ¡ri StefÃ¡nsson, chief executive of deCODE Genetics, in the Nature article. “The more mutations we pass on, the more likely that one of them is going to be deleterious.”
Genes are also important in the sense that they are the guide to producing proteins and helping the human body develop, grow, and function correctly.
In the project, scientists studied genetic material from the blood samples of 78 parent-child trios, made up of the child, father, and mother. They analyzed families whose parents had no signs of mental disorder, but who gave birth to a child who displayed symptoms of autism or schizophrenia. It gave researchers the opportunity to isolate brand-new mutations, which occur near conception or spontaneously, in genes of a child that were not seen before in the parents. These de novo mutations appear in approximately 20 to 30 percent cases of autism.
“This study provides some of the first solid scientific evidence for a true increase in the condition,” Dr. Fred R. Volkmar, director of the Child Study Center at the Yale School of Medicine unaffiliated with the study, told the New York Times. “It is extremely well done and the sample meticulously characterized.”
The Los Angeles Times states that the report´s results also go against past assumptions that the age of the mother was the leading factor in identifying development problems in children. The authors described how the risk of chromosomal abnormalities could increase with older mothers, but a large amount of the genetic risk is found in the sperm rather than the egg. In particular, an average child of a 20-year-old father had 25 random mutations that were associated with paternal genetic material, while there were 65 mutations in the child of a man of 40 years of age.
When the researchers took away the element of paternal age, they discovered that there was no difference in genetic risk for those who were diagnosed with autism or schizophrenia in the control group of Icelanders.
“It is absolutely stunning that the father´s age accounted for all this added risk, given the possibility of environmental factors and the diversity of the population,” commented study senior author Stefansson in the New York Times article. “And it´s stunning that so little is contributed by the age of the mother.”
According to the New York Times, experts believe that the study may influence decisions by males on having more children later in life.
“If the paternal-age effect on the de novo mutation rate does lead to substantially impaired health in the children of older fathers, then collecting the sperm of young adult men and cold-storing it for later use could be a wise individual decision,” Alexey Kondrashov, a professor of evolutionary biology at the University of Michigan in Ann Arbor, wrote in an accompanying editorial.
Experts have disagreed with Kondrashov, stating that it is not necessary to bank their sperm to help their future children from developing the disease.
“Whilst sperm banking is technically feasible, more data would be required to recommend this policy as routine," Christopher Barrett, an expert in reproductive medicine at Dundee University, told The Telegraph.
Other experts believe that males do not necessarily need to consider delaying parenthood as a result of the findings of the study.
“It is a surprise to find that men transmit a higher number of mutations to their children than do women,” Dr. Allan Pacey, Chairman of the British Fertility Society, commented in the Telegraph article. "Whilst not wanting to scare the children of older fathers, information like this is important to understand and should remind us that nature designed us to have our children at a young age and if at all possible men and women should not delay parenthood if they are in a position not to.”
For men who are in their 40s or older, the risk is about two percent. There are other associated biological factors that are not completely known. Researchers believe that it is up to the individual to decide on what route to take with reproductive processes.
“You are going to have guys who look at this and say, ℠Oh no, you mean I have to have all my kids when I´m 20 and stupid?´” noted Evan E. Eichler, a University of Washington professor of genome sciences, in the New York Times article. “Well, of course not. 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.”