February 27, 2014
Older Fathers Linked To Higher Risk Of Cognitive, Behavioral Issues In Their Offspring
Brett Smith for redOrbit.com - Your Universe Online
A large new study conducted by a team of American and Swedish researchers has found a connection between paternal age and the risk of a child developing cognitive or behavioral problems.
"We were shocked by the findings," said study author Brian D'Onofrio, an associate professor of psychology and brain sciences at Indiana University Bloomington.
"The specific associations with paternal age were much, much larger than in previous studies,” D’Onofrio added. “In fact, we found that advancing paternal age was associated with greater risk for several problems, such as ADHD, suicide attempts and substance use problems, whereas traditional research designs suggested advancing paternal age may have diminished the rate at which these problems occur."
Published in JAMA Psychiatry, the study was based on a massive data set: everyone born in Sweden from 1973 to 2001. The study team found that a child born to a 45-year-old father is 3.5 times more likely to develop autism, 13 times more likely to develop ADHD, twice as likely to develop a psychotic disorder, 25 times more likely to receive a diagnosis for bipolar disorder and 2.5 times more likely to exhibit suicidal behavior or a substance abuse problem when compared to a child with a 24-year-old father.
For most of these issues, the odds of development increased steadily with paternal age, indicating there is no age threshold at which childbearing suddenly becomes riskier.
The study team compared siblings in their research, which considers factors for children living in the same house to be very similar. When they did this, they found that the connections with advancing paternal age were much stronger than for the general population. The team also compared the development of first-cousins to control for sibling relationships and birth order.
The authors also considered parents' highest level of education and income, because older parents are considered to be more mature and financially secure. However, the findings were extremely consistent, as the connections between mental problems and advancing paternal age continued.
"The findings in this study are more informative than many previous studies," D'Onofrio said. "First, we had the largest sample size for a study on paternal age. Second, we predicted numerous psychiatric and academic problems that are associated with significant impairment. Finally, we were able to estimate the association between paternal age at childbearing and these problems while comparing differentially exposed siblings, as well as cousins.”
“These approaches allowed us to control for many factors that other studies could not,” he concluded.
The conclusions of the study are particularly troubling as the average age for having a child has been escalating for both men and women over the last four decades. For men the average age is three years older than it was in 1970, according to the study researchers. They noted that the implications of this trend are yet to be understood.
"While the findings do not indicate that every child born to an older father will have these problems," D'Onofrio said, "they add to a growing body of research indicating that advancing paternal age is associated with increased risk for serious problems. As such, the entire body of research can help to inform individuals in their personal and medical decision-making."