Children born to older fathers are at higher risk for various psychiatric and learning problems than once thought, a large new study suggests.
Among more than 2 million children born in Sweden, researchers found that those born to fathers aged 45 and older were more prone to problems such as autism, attention-deficit/hyperactivity disorder (ADHD), bipolar disorder, schizophrenia, attempted suicide and drug abuse. Other problems include poor grades in school and low IQ scores.
"We were shocked by the findings," lead researcher Brian D'Onofrio, an associate professor in the department of psychological and brain sciences at Indiana University, said in a university news release. "The specific associations with paternal age were much, much larger than in previous studies."
D'Onofrio, however, doesn't want people to think that all or even most children of older fathers will have these problems.
"We are not saying that all children born to older fathers will have psychiatric or educational problems," D'Onofrio said in an interview.
"Rather, the study found that advancing paternal age at childbearing is associated with greater risk for serious problems," he said. "As such, the study adds to a growing body of research that suggests families, doctors and society as a whole must consider both the pros and cons of delaying childbearing."
While the new study uncovered an association between older fathers and increased risk of mental health and learning problems in their children, it didn't prove cause-and-effect.
And a child behavioral specialist not involved with the study said the findings should be kept in perspective because the actual risk of having a child with any of these problems is small.
The new report was published in the Feb. 26 online edition of JAMA Psychiatry.
For the study, D'Onofrio and colleagues collected data on about 2.6 million children born in Sweden from 1973 to 2001.
Compared with a child born to a 24-year-old father, a child born to a 45-year-old father was 3.5 times more likely to have autism and 13 times more likely to have ADHD, the study found.
In addition, children born to 45-year-old fathers were twice as likely to have a psychotic disorder, 25 times more likely to have bipolar disorder and about 2.5 times more likely to have suicidal behavior or a drug abuse problem, the authors noted.
Over the past 40 years, the average age when men and women start a family has been increasing. In the United States, the average age for mothers having their first baby has gone up about four years, from 21.5 to 25.4 years old, the news release noted. For men the average increase is three years.
An expert not involved with the study said parents shouldn't overreact to the findings.
"There have been studies before that have shown an association between advanced parental age and developmental problems, particularly autism," said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Steven and Alexandra Cohen Children's Medical Center of New York.
"Parents need to remember that many of the conditions the researchers looked at are very uncommon, and even if you double the risk, the likelihood is you are not going to have a child affected with any of these conditions," he said.
Other studies have shown that women who are older when they first have children also run the risk of having kids with similar problems, such as autism, Adesman said.
Although the reasons for this risk are not known, Adesman said that when a female child is born she has all the eggs she will ever have and it's possible that older eggs are more prone to genetic changes as women delay childbirth. The same may also be true of the sperm that older men produce, he said.
"Age seems to have some adverse impact in terms of increasing the risk of children having developmental problems. But age is just one of many factors that couples need to consider when planning a family," Adesman said.
Although these problems were found to happen more often with older dads, there is no specific age when the risk starts to increase, the researchers noted.