Older men are more likely to have children with autism, OCD and schizophrenia, according to Professor Luke O’Neill.
The Trinity professor said new studies have shown that sperm can “go off” as you age – with sperm becoming less viable every year after a man turns 40.
He said the risks of neurological issues and problems with conception increase every five years a prospective father ages.
Prof O’Neill said the findings are included in a comparative analysis of 90 different studies involving 93,800 men.
“What they found was the rate of swimming goes down as they age,” he said. “The sperm get less motile is what we call it and then they get more misshapen as you get older.
“With every five years, basically, the sperm changes. Over 40 seems to be a turning point. So, men after 40, every year that goes by, their sperm is less viable.”
He said there are two main reasons for the deterioration in sperm – an increase in DNA errors and an increase in chemical stains.
“You make sperm from a previous sperm,” he said. “So the sperm divides and you have two sperms and the DNA gets copied.
“Every time the sperm divides, errors creep into the DNA and they will build up over time.
“That’s why, say you’re 50 for instance, there will be slightly more errors in the sperm than when you were 30.
“The second thing is the DNA then gets marked as you get older,” he continued. “These chemical stains build up and as you age of course more and more marks happen.
“So, the older you are then, it is kind of like a perfect storm, there are more mutations and there are more stains on the DNA and then when the egg gets fertilised then that translates into effects.”
Prof O’Neill said the studies have shown a range of different impacts on sperm as a man ages.
“They have shown that older men are more likely to have children with autism and schizophrenia,” he said. “There is an increased rate of that.
“Every five years older the man is, the risk of those goes up.
“The part of the DNA that controls brain development seems to be changing and that could explain then why, with older sperm, there is a higher risk of these neurological-type conditions.”
The Trinity professor said studies have also shown that the risk of miscarriage and difficulties conceiving also go up with a father’s age.
He said it may be possible to remove stains and correct DNA errors in the future.